Gemology/Gemmology in forensic science .pptx

In this presentation, I have aimed to describe various physical and chemical properties of gemstones that are of use in traditional gemstone studies as well as in the aspects of forensic science.
Beginning from a brief history of how gemology or gemmology evolved from a hobby into a full fledged science and ending at X-ray diffraction studies (brief)

1. Gemmology Bhanu Pratap singh Yadav Crime Scene Management & Physical Evidences NFSU– Delhi Campus

2. Contents: Introduction to Gemmology: Origin, Development and Scope Gemstone Examination: Physical Methods Optical Methods Fluorescence Techniques Spectroscopic Techniques X-Ray Diffraction Studies

3. Introduction to Gemmology The scope of gemmology encompasses a multifaceted range of activities, including the identification and classification of gemstones based on their distinct properties, the exploration of geological processes influencing their formation, and the valuation of gemstones considering factors such as rarity and clarity. Gemmologists play a crucial role in detecting treatments or enhancements applied to gemstones and collaborate with jewelers in crafting aesthetically pleasing jewelry designs. Moreover, staying informed about market trends is essential in navigating the dynamic gem industry. From a forensic standpoint, gemmology assumes a pivotal role in authenticating gemstones, detecting fraud or substitution, and providing expertise in crime scene analysis. The ability to trace the origin and history of gemstones contributes to establishing ownership and uncovering potential involvement in criminal activities. Furthermore, gemmologists engaged in forensics scrutinize documentation, such as certificates and receipts, to verify authenticity and offer expert testimony in legal proceedings related to gemstone crimes. In essence, the forensic scope of gemmology ensures precision and accountability in the examination and analysis of gem-related evidence within a legal context. What is Gemmology? Gemmology is the science of studying natural and artificial gemstones, their properties, characteristics, identification, grading, and valuation. Gemmologists are experts who can examine, appraise, and certify gemstones and jewelry.  Gemmology is a branch of mineralogy and geology, and it requires specialized knowledge and equipment. 20XX 3 Scope of Gemmology

4. Introduction to Gemmology Origin of Gemmology Gemmology, the science dedicated to the study of gemstones and their technical aspects for identification purposes, has a rich history spanning over 2000 years. While early observations date back to philosophers and scientists captivated by the beauty of gems, it wasn't until the latter half of the 19th century that gemmology emerged as a specialized branch, branching off from mineralogy. The science gained significance in identifying modern synthetic gems, leading us to the exploration of its historical milestones. 2023 History & Development

5. 20XX presentation title 5 Taaffeite

6. 20XX 6 Tanzanite Gemstone Refractometer

7. Origins of Gems: Gemstones derive their origin from diverse geological processes shaping the Earth's crust and mantle. Sedimentary, igneous, and metamorphic processes each contribute uniquely: Sedimentary rocks lack primary gem material except for organic substances like Amber and jet but may form secondary deposits if weathered rocks carry heavier minerals, seen in Brazil, Myanmar, and Sri Lanka as water-worn pebbles. Opals originate from silica-bearing water solidifying in rock crevices. Intrusive igneous rocks house vital gem minerals like feldspar, quartz, and tourmaline, forming sizable crystals through gradual cooling and fractional crystallization. Pegmatites and geodes exemplify intrusive gem-bearing rocks. Metamorphic rocks yield gems like emerald, alexandrite, ruby, sapphire, garnet, etc. through chemical reactions with molten magma. Shearing and crushing result in gems like garnet and jadeite. Diamonds crystallize in the Mohorovičić discontinuity or Moho, a crust-mantle transitional zone deep beneath the Earth's surface. They ascend through volcanic eruptions, solidifying into kimberlite pipes. Over time, erosion transforms pipes into hillocks, releasing diamonds into alluvial deposits along riverbeds and coastal strips.  In essence, gemstone genesis intertwines with sedimentary, igneous, and metamorphic processes, showcasing the Earth's geological wonders that shape these treasures. Minerals, Rocks and Gemstones: Mineral: Formed within the Earth, inorganic substance with constant properties. Only about sixty minerals qualify as gem materials due to beauty, rarity, and durability. Precious metals like gold and platinum, along with diamond, are chemical elements. Rocks: Mixtures or aggregates of minerals, forming the Earth's crust. Examples include granite. Gem Materials: Limited to about sixty minerals meeting criteria for beauty, rarity, and durability. Precious metals and diamond stand out as chemical elements. Gemstones are primarily single-mineral entities, with exceptions like lapis lazuli 20XX 7

8. Introduction to Gemmology Gems are found or mined in distinct geological settings, such as gem gravels, gem-bearing veins, or diamond pipes. Location of discovery is crucial for mineralogists as it offers insights into the processes of gemstone formation. Direct Deposit: Many gemstones are discovered near their original formation site. This type of deposit provides valuable evidence for understanding the methods of gemstone formation. Alluvial Gem Deposits: Result from gems being transported away from their formation sites. Agents include weathering forces like wind or rain and river flows. Alluvial gems often exhibit abrasions on surfaces, indicating the distances traveled. Residual Deposits (Eluvial): Gems released by weathering may settle with little transportation or concentration. These deposits, known as eluvial, showcase gems finding a resting place near their parent rocks. Signs of Transport: Abraded surfaces observed in water-worn topaz pebbles and rounded profiles of diamond crystals from Namibian coastline. Geological Insights: The geological context of gemstones serves as a rich source of information about their origins. Direct deposits and alluvial displacement offer unique perspectives on the dynamic processes shaping precious stones. 20XX presentation title 8 Gem Occurrences

9. Hydraulic Mining: Water jets dislodge gem material from overburden. Channels on hillsides direct pressurized water to split rocks, washing gem-laden gravel downhill. Discontinued due to severe environmental impact. River Panning: Collection of gemstones during river or stream gravel washing. Pans filled with water settle heavy material, using riffles for gem separation. Labor-intensive with lower success rates. Open Pit Mining: Conducted under Gemologist guidance, removing layers to expose rocks for gem extraction. Cost-effective, results in landfill areas after mining completion Strip Mining: Like open-pit mining, involving drilling, blasting, and sequential strip removal. Strips filled with dirt, and top layer levelled for future land use. Mountaintop Removal Mining: Involves clearing mountain tops, blasting with dynamite, and retrieving gemstone-rich rocks. Displaced dirt is dumped into valleys using bulldozers. Quarrying: Environmentally less hazardous method used for building materials. Rocks drilled or blasted for various uses, with gemstones extracted during subsequent processing. Borehole Mining: Deep holes drilled into the plain land, where water is used to break down rocks and create a gemstone-bearing slurry. Environmentally friendly and adaptable to shifting locations. Drift Mining: Conducted on mountain sides, with horizontal tunnels or drifts created. Gravity aids in the material's descent for easy retrieval. Shaft Mining: Vertical tunnels or shafts created below mountains for miners' movement and material extraction. Costly but effective method for deep gemstone extraction. Slope Mining: Shafts made slanting and parallel to the ground for situations where straight shafts are challenging. Conveyor systems transport broken rocks for processing. Hard Rock Mining: Tunnels made inside the ground, often referred to as A dits , with shafts extending vertically using explosives. Most dangerous method, creating different floors for various purposes, including gemstone extraction. 20XX presentation title 9 Gemstone Mining Techniques Surface Mining Underground Mining

10. Crystallography Determinants of Crystal Properties: - Determined by symmetry and structure. - Higher crystal symmetry implies more non-directional properties. - Lower crystal symmetry results in more directional properties. Crystal Symmetry and Space Lattice: Crystal symmetry = a regular arrangement of atoms in three dimensions; linked to the space lattice. Described by a unit cell, the smallest repeating unit of the lattice. 14 Bravais lattices categorize any crystal structure. These lattices belong to seven crystal systems based on unit cell shape and angles. Understanding crystallography principles is crucial for gemstone professionals, guiding them in cutting, cleaving, and polishing processes. The arrangement of atoms in crystalline minerals and the forces governing this arrangement play a pivotal role in determining the physical and optical properties of gemstones. Crystallography is the scientific study of the arrangement of atoms in solids, especially crystals. Crystals are solids that have a regular and repeating pattern of atoms or molecules, forming a three-dimensional structure called a crystal lattice. Crystallography can reveal the shape, size, symmetry, and composition of crystals, as well as their physical and chemical properties. Crystallography is an important branch of science that has applications in many fields, such as materials science, solid-state physics, chemistry, biology, geology, and medicine. Use in Gem Cutting and Polishing: - Diamond cleavers leverage crystallography knowledge to split stones along cleavage planes. - Lapidaries consider crystallography when placing facets to avoid directions of maximum hardness and enhance color in gemstones. - Avoiding polishing facets parallel to cleavage planes prevents uneven surfaces or gem cleavage during polishing. 2023 10 Importance of Crystallography

11. The atomic structure of a crystal Illustrating the concept of minute elementary blocks, Haüy proposed crystals grow through the assembly of tiny units or building blocks. This theory finds practical validation in the cleavage rhombohedron of Iceland spar calcite, which, when broken down, reveals identical copies of the parent structure down to the molecular level. The fundamental building block, termed the "unit cell," represents the smallest lattice structure retaining all mineral characteristics, shaped by chemical composition and valency forces. Crystal nucleation and growth involve processes akin to salt crystal formation from a saturated solution, emphasizing factors such as saturation, evaporation, and cooling. The parallel extends to mineral crystal growth from molten or aqueous solutions in the Earth, influencing crystal sizes in rocks and the formation of geologically recognized cavities like geodes, druses, or vugs .  In 1669, Nicolas Steno discovered that quartz crystal interfacial angles remain consistent across crystals, a groundbreaking revelation extending to various minerals. Abbé Haüy deemed the ' father of crystallography ,' mathematically established that each substance possesses a distinct, unique form, postulating orderly internal structures behind their external conformity. 20XX presentation title 11 René Just “ Abbé ” Haüy 1743-1822

12. All solid matter falls into the categories of either crystalline or non-crystalline, or a combination of both. The term "crystalline" originally derived from the Greek word " krystallos ," meaning ice, later expanded to describe any substance with the clarity of ice, even if not colorless or transparent. Non-Crystalline Substances: Atoms and molecules are randomly arranged, lacking a specific order or pattern. Cannot develop a characteristic shape due to the absence of alignment. Examples include glass, amber, and jet, with glass containing disordered silicon tetrahedra frameworks. Crystalline Substances: Atoms and molecules exhibit an ordered and symmetrical three-dimensional pattern. External shape often reflects the underlying crystal structure, visible in mineral specimens. Examples include most minerals, with notable exceptions like opal, and various non-mineral substances that can form crystals. Non-Directional Properties (Scalar/Isotropic): Independent of measurement direction. Examples: density, specific heat, thermal conductivity, and electrical resistivity. Associated with metals featuring non-directional or isotropic bonding. Directional Properties (Tensor/Anisotropic): Dependent on the measurement direction. Examples: refractive index, elastic modulus, piezoelectricity, and optical activity. Associated with non-metals like insulators and semiconductors with directional or anisotropic bonding Directional Properties in Crystalline Materials: - Physical characteristics vary with crystal orientation, a feature absent in non-crystalline substances. - Diamond serves as an example with directional-dependent properties like cleavage and hardness. - Optical properties, including color, can also vary with viewing direction in colored gems like ruby and sapphire. 20XX presentation title 12 Crystalline and Non-Crystalline Materials

13. Symmetry in Crystals In crystallography, symmetry is crucial for defining the structure of crystals, especially in gemmology. Gem crystals are classified into seven systems based on their varying symmetry levels, ranging from highly symmetrical cubic to less symmetrical triclinic systems. While gemmological tasks focus on recognizing crystal habits and understanding optical and physical traits, a solid grasp of imaginary crystallographic axes and symmetry elements is essential. Imaginary crystallographic axes act as a reference for describing a crystal's idealized shape, intersecting at the 'origin' point and aiding in identifying crystal faces based on angles and lengths. Three essential elements of symmetry contribute significantly to crystallography. These elements include: Axis of Symmetry: An axis around which a crystal can be rotated to a position where it appears unchanged. Plane of Symmetry: A plane that divides a crystal into two identical halves, reflecting symmetrical properties. Centre of Symmetry: A point within the ideal crystal where lines drawn from any point through the center to the opposite point result in identical lengths and angles. presentation title 20XX 13 An axis of Symmetry A plane of Symmetry

14. 20XX presentation title 14 Crystal systems The Seven Crystal Systems and their Elements of Symmetry As mentioned earlier, crystals can be grouped into seven systems. These can be further subdivided into 32 classes. The subdivision is based on the different degrees of symmetry (as specified by the elements of symmetry) of the crystals within each system. The seven crystal systems themselves are classified in terms of the number of their crystal axes, their relative lengths, and the angles between them. The elements of symmetry included in the following descriptions of the seven crystal systems refer to the highest level of symmetry in each case (it should be remembered that crystals do form with lower levels of symmetry and may sometimes have no center of symmetry at all).

15. The Cubic Syste m Crystals in this system have the highest order of symmetry and are also called isometric. The cubic system has three crystal axes (a1, a2, a3), all of which are of equal length (a1 = a2 = a3) and intersect each other at right angles (90°). Axes of symmetry: 13 (six 2-fold, four 3-fold, three 4-fold) Planes of symmetry: 9 Centre of symmetry: 1 Common forms: cube, eight-sided octahedron, twelve-sided dodecahedron Examples: diamond, garnet, spinel, fluorite presentation title 20XX 15

16. presentation title 20XX 16 The Tetragonal System This has three crystal axes. The two lateral ones are of equal length (a1 = a2) and at right angles (90°) to each other. The third (principal or c) axis is at right angles (90°) to the plane of the other two and is shorter or longer than them (c ≠ a1) Axes of symmetry: 5 (four two-fold, one four-fold) Planes of symmetry: 5 Centre of symmetry: 1 Common forms: four-sided prism with square cross-section Examples: zircon, scapolite

17. The Hexago nal System Contains four crystal axes, the three lateral ones are of equal length (a1 = a2 = a3) and intersect each other at 60° in the same plane. The fourth (or principal) c-axis is at right angles to the other three and is usually longer. Axis of symmetry: 7 (six two-fold, one six-fold) Planes of symmetry: 7 Centre of symmetry: 1 Common forms: six-sided prism Examples: beryl, apatite 20XX presentation title 17

18. The Tri go nal/Rhombohedral System This system (sometimes treated as a subdivision of the hexagonal system) has four crystal axes which are arranged in the same manner as in the hexagonal system. The symmetry of the trigonal system is, however, lower than that of the hexagonal system. Axes of symmetry: 4 (three two-fold, one three-fold) Planes of symmetry: 3 Centre of symmetry: 1 Common forms: three-sided prism, rhombohedron Examples: calcite, corundum, quartz, tourmaline 20XX presentation title 18

19. The O rthorhombic System This system has three crystal axes, all at right angles (90°) to each other and all having different lengths (a b c). The principal or c axis is the longest, and of the remaining two lateral axes, the longer b is known as the macro axis and the shorter a is called the brachy axis. Axes of symmetry: (three two-fold ) Planes of symmetry: 3 Centre of symmetry: 1 Common forms: rectangular prism (prism with cross-section of playing card ‘diamond’), bipyramid comprising two four-sided pyramids joined at the base Examples: topaz, peridot, chrysoberyl, andalusite, sinhalite, zoisite 20XX presentation title 19

20. The Monoclinic System There are three crystal axes in this system, all of unequal lengths (a ≠ b ≠ c). The b axis, known as the ortho axis, is at right angles to the plane of the other two which cut each other obliquely. The longest of these is the c axis, and the one inclined to it (at an angle other than 90°) is called the a or clino axis. Axes of symmetry: (one two-fold ) Planes of symmetry: 1 Centre of symmetry: 1 Common forms: prisms and pinacoids Examples: orthoclase feldspar (moonstone), diopside 20XX presentation title 20

21. The Triclinic System This system has three crystal axes, all of unequal lengths (a b c) and all inclined to each other at angles other than 90°. The longer lateral axis is called the macro, and the shorter is called the brachy as in the orthorhombic system Axes of symmetry: none Planes of symmetry: none Centre of symmetry: 1 Common forms: prism (tilted sideways and backwards) with pinacoids Examples: plagioclase feldspar, microcline feldspar (amazonite), rhodonite, turquoise (usually in microcrystalline aggregates) 20XX presentation title 21

22. Crystal Form: A crystal form is composed of a group of crystal faces which are similarly related to the crystal axes. A form made up entirely of identical interchangeable faces is called a closed form (e.g. a cube or an octahedron). A form which is only completed by the addition of other forms is called an open form. An open form cannot exist on its own and must be completed by the addition of other open forms which act as suitable terminations to complete shape. 20XX presentation title 22

23. Crystal Habit: The shape in which a mineral usually crystallizes is referred to as its habit. From the sketches illustrating the seven crystal systems it can be seen that minerals belonging to the same system can often have very different habits, despite the similarity of their internal crystal structures. These differences in habit can be the result of combinations of more than one form. Other differences may be due to the variety of terminations which some crystals adopt. Some of the more bizarre shapes are caused by the parallel growth or interpenetration of two or more crystals. The many differences in crystal habit can be confusing at first encounter, as it is often difficult to associate a habit with the idealized shape of one of the seven systems. This very factor can sometimes be an advantage, however, as it can be used to identify a mineral simply by the individuality of its habit. Sometimes the shape of a crystal is due to influences which modify its normal habit 20XX presentation title 23 Examples of a few crystalline habits:

24. Twinned Crystals: A twinned crystal consists of two or more individual crystals that have grown together in a crystallographic relationship to produce a symmetrical shape. Twinning, which is very common with quartz crystals, usually occurs in one of two forms: Contact Twins: These occur when the twin-halves of a crystal have grown with one half rotated through 180° to the other half. Spinel and diamond often occur in this form. With diamond, a contact twin is called a macle . Interpenetrant Twins: consist of two or more crystals which have grown in proximity and have penetrated each other with a direct relationship between their axes. Common examples can be seen in the interpenetrant cubes of fluorite, and in staurolite twins. presentation title 20XX 24 Contact Twins Interpenetrant Twins

25. Gemstone Examination Physical Methods Fluorescence and Spectroscopic techniques Optical Methods X-Ray Diffraction Studies Gemmology 2023 25

26. 20XX presentation title 26 Cleavage, in mineralogy, refers to the propensity of a crystallized mineral to break along specific directions, yielding relatively smooth surfaces. This phenomenon results from weak cohesive forces within the mineral along different directions and is influenced by the mineral's form and crystal structure. Crystals may exhibit cleavage in more than one direction, and a crystal cleaving in one direction will do so equally well in any parallel plane. Cleavage planes align with the crystal structure and are parallel to potential crystal faces. This splitting is attributed to the regular arrangement of atoms, rendering amorphous substances devoid of cleavage.  Physical Properties: Cleavage in Gemstones Identification of cleavage: observing minutely stepped flat planes or a wavy pattern on the mineral's surface. The presence of a pearly luster indicates its laminated nature. Iridescent colors along cleavage directions or cracks may develop due to air penetrating flaws. Smooth parallel cracks or directional cracks in cut specimens signify cleavage directions. A gem cutter considers cleavage when selecting a cut type to avoid flaws or cracking. Cleavage is especially useful in cleaving rough stones like diamonds to enhance yield and reduce costs. Octahedral cleavage occurs parallel to octahedral faces in cubic crystals (e.g., diamond). Prismatic cleavage aligns with the prism face (e.g., spodumene). Basal cleavage is parallel to the basal pinacoid (e.g., topaz). Rhombohedral cleavage occurs parallel to rhombohedral faces (e.g., calcite). Perfect cleavage is exemplified by minerals like mica, topaz, or calcite. Easy but imperfect cleavage, as seen in octahedral cleavage in fluorite. Easy and perfect cleavage, exemplified by rhombohedral cleavage in calcite. Difficult cleavage, as observed in peridot. Perfect but difficult cleavage, such as octahedral cleavage in diamond. Difficult and imperfect cleavage, like the basal cleavage in beryl. Types of Cleavage: Types of Cleavage based on Quality:

27. 20XX presentation title 27 Cleavage is a directional feature and can only exist in crystalline substances. Cleavage occurs in a gemstone as a well-defined plane of weak atomic bonding which allows the stone to be split in two leaving reasonably flat surfaces. These cleavage planes are always parallel to a crystal face in a perfectly formed single crystal. The gemstones that possess the property of cleavage, the cleavage planes are the result of the atoms lying parallel to these planes being more closely linked together than the atoms between the planes. The bonding force along the planes of atoms is therefore much stronger than between the planes.

28. 20XX presentation title 28 Physical Properties: Parting Fractures Parting (false or pseudo-cleavage): Some minerals which do not possess cleavage properties can be divided in two along a plane of weakness rather than along a plane related to the stone’s crystal faces. Such a direction of weakness is called a parting plane. Parting is usually caused by a form of twinning. In the case of corundum and labradorite, parting occurs along directions of lamellar twinning. A significant difference between parting and cleavage is that Parting only occurs at discrete intervals along the twinned crystal, while cleavage planes are separated only by atomic layer intervals. Parting is usually due to lamellar twinning, as in  labradorite feldspar . Parting is possible only along definite planes in twinned crystals and not along every parallel plane. A crystal may exhibit both cleavage and parting, as in  corundum , (parting parallel to the rhombohedral face and cleavage parallel to the basal pinacoid) and  labradorite  (parting along the lamellar plane and two other directions of cleavage).

29. 20XX presentation title 29 Fracture: The way in which a mineral breaks (other than by cleavage or parting) is known as fracture. Unlike cleavage and parting, fracture occurs in a random direction, often as the result of a sharp impact. It is typical of non-crystalline materials such as glass but can also occur in those crystalline materials which do not have significant planes of cleavage or weakness (e.g. quartz and beryl). Fracture can also happen occasionally with other crystals, even (as indicated earlier) with diamond. Sometimes the surface contour of a fracture can be distinctive enough to constitute a useful identifying feature Types of fracture, together with the gem materials in which they occur, are as follows: Conchoidal: This is a shell-like fracture consisting of a series of scalloped rings similar to those seen in a seashell. Conchoidal fractures occur in quartz and the garnets. It is particularly characteristic of glass. Hackly or splintery: This takes the form of long fibrous splinters and can be seen in nephrite, jadeite and ivory. Smooth or even: This type of fracture, although not perfectly flat, shows no signs of significant irregularities. Examples of smooth fractures can often be seen in rough diamonds

30. Physical Properties: In gemmology and mineralogy, it is a measure of a gemstone's ability to resist abrasion . A gemstone's hardness must be taken into consideration for durability, in addition to rarity and beauty, when selecting it for use in jewellery . A gemstone's ability to resist abrasion is not due to the hardness characteristic of its atoms, but rather to the strength of the bonds between these atoms. Microscopic particles of silica or quartz in airborne dust constantly test a gem's durability by gradually abrading its polished surface. The reason for this is that the gem must be capable of withstanding the wear and tear to which jewellery is subjected in everyday use. While a ring-mounted gemstone may have to endure the occasional hard knock, it is the presence in airborne dust of microscopic particles of silica or quartz that is the real test of a gem’s durability. These particles are in continual contact with the gem, and if the stone is relatively soft they will gradually abrade its polished surface. Hardness Specific Density Density and Relative Density 20XX presentation title 30 Hardness:

31. 20XX presentation title 31 Mohs' Scale of Comparative Hardness: Mohs' scale is a method for assessing the hardness of minerals, developed by German mineralogist Friedrich Mohs in 1822. It measures a material's resistance to abrasion when subjected to a pointed fragment of another substance at a pressure lower than that causing cleavage or fracture. The scale is purely comparative, with divisions not evenly spaced. Friedrich Mohs chose ten common minerals as standards, numbered from one to ten based on ascending hardness. These minerals were selected for their distinctive hardness and easy availability in a high state of purity. The chosen minerals are: While hardness is crucial for durability, it is not the sole factor. Brittleness also plays a role; for instance, Zircon, despite its hardness of 7 to 7.5, can be brittle, leading to 'paper wear.’ In contrast, jade minerals (nephrite and jadeite) exhibit toughness due to their microscopic interlocking fibers or crystals, making them durable tools for prehistoric man.

32. 20XX presentation title 32 Hardness pencils , with pointed fragments of minerals adhered to wood/metal holders, follow Mohs' scale standards. Starting with the softest pencil and progressing, the gem is scratched, and the hardness lies between the scratches. R everse hardness test: A safer alternative, where the gem's facet edge or girdle is drawn across plates of known hardness. The stone's hardness falls between the unscratched plate and the preceding one. Hardness plates: made from orthoclase, quartz, synthetic spinel, and synthetic corundum are used for testing. Synthetic corundum sections serve as a confirmatory test for diamond. Scratch Test on Glass Slides: A series of scratch tests on a glass microscope slide using minerals provides insights into relative hardness via varied depths of scratches . A glass microscope slide serves as a simple, non-destructive reference guide for estimating a gem's hardness. Hardness Tests in Gemmology: Hardness Pencils

33. Physical Properties: Specific Gravity (SG): It represents the ratio of the weight of a substance to the weight of an equal volume of pure water, measured at standard atmospheric pressure and 4°C , the temperature at which water is most dense. SG is a dimensionless ratio, expressed without units. The SG of a material like diamond, for instance, being 3.52, means it is 3.52 times heavier than an identical volume of water. Water is the chosen standard with an SG of 1.0. Density: It is the weight per unit volume of a substance , measured in units of weight and volume. In the International System of Units (SI), density is expressed in kilograms per cubic meter (kg/m³). For diamond, the density is 3520 kg/m³, equivalent to 3.52 g/cc in older textbooks. Relative Density : In the context of liquids, relative density, like SG, is the ratio between the weight of the liquid and the weight of an equal volume of water at 4°C . Specific Gravity Density & Relative Density 20XX presentation title 33

34. 20XX presentation title 34 Measurement of Specific Gravity: Principle: based on Archimedes’ principle which states that a body submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. Calculation of Specific Gravity (SG): However, for use with gemstones due to their comparatively smaller volumes, more accurate SG bottle, called a pycnometer , consists of a small glass phial having a ground-glass stopper through which runs a capillary channel. At the gemmologists' laboratories, more sophisticated methods are used, like single-pan, two-pan, and spring balance method for SG estimation. A pycnometer Single-pan SG balance Two-pan SG balance Spring Balance method

35. Optical Properties: Colour Lustre Sheen Reflection & Refraction Polarization & Pleochroism Luminescence presentation title 20XX 35

36. Colour of Gemstones: The beauty of appearance was given as a prime quality of a gemstone. In a world where colour is one of the dominant visual sensations, it is not surprising that a gemstone’s beauty is largely determined by its colour. Although the perception of colour is an everyday experience, and as such is taken for granted, in gemmological studies it is important to understand exactly how the appearance of colour is produced in a gemstone. The following are some ways which produce “colors” in gemstones: Selective absorption and Gemstone coloration. Color-change gemstones and Alexandrite effect. Coloration due interference & dispersion. Color- centres and gemstone coloration. 20XX presentation title 36

37. Selective Absorption & Gemstone Coloration: Selective absorption: The suppression of certain wavelengths or colors from the white light illuminating an object is known as selective absorption. It can be visually analyzed using an instrument called a spectroscope. 37 A gemstone having an absorption band in the blue/violet end of the spectrum (such as a cape series diamond) the residual red and green part of the white light reflected from the stone gives it a yellow appearance White light consists of a balanced mix of all visible spectrum colors. When observing a colored gemstone in white light, the perceived color results from the stone selectively absorbing specific wavelengths or bands of wavelengths from the original light. In transparent stones, absorption occurs as light passes through, while in opaque stones, it happens during reflection from the surface layer. The overall color appearance stems from the combined effect of the remaining unabsorbed parts of the white light spectrum, creating a complementary color to the absorbed wavelengths. An absorption spectrum showing three bands (caused by iron) which are diagnostic for blue sapphire The Visible Spectrum

38. 20XX presentation title 38 Allochromatic Gemstones: These exhibit selective absorption due to impurities present in their composition. Ex- Cr oxide in ruby or Fe oxide in aquamarine are examples of impurities causing coloration. Most colored gemstones fall under this category. In their pure state, some allochromatic gems exist as colorless varieties. Rock crystal, colorless sapphire, topaz , etc. have no intrinsic coloration. Idiochromatic Gemstones: These owe their color to chemicals within their own composition. Ex- Cu in turquoise or Mn in spessartite garnet. Idiochromatic gems derive color from their inherent chemical makeup, distinguishing them from allochromatic counterparts influenced by impurities. Selective absorption is mainly caused by 8 metallic transition elements . In allochromatic gems, these elements act as colouring impurities, while in idiochromatic stones, they are integral to the mineral's chemical formula. Zircon and certain topaz, quartz, and fluorspar varieties lack measurable transition elements, making their colors more susceptible to change through heat and irradiation. T ints V ary C hromatically, M an I C ould N ever C opy!

39. Colour-Change Gemstones & Alexandrite Effect: Alexandrite Simulants: Due to its rarity, various simulants have been introduced to mimic alexandrite's color -change effect, such as synthetic corundum doped with vanadium and green synthetic spinel. Synthetic Alexandrites: True synthetic replicas of high-quality Siberian alexandrite were introduced in 1973, but they are costlier than corundum-based simulants. Identifying and distinguishing synthetic alexandrites from natural gemstones is a challenge for gemmologists. Occurrence in Other Stones: Although rare, colour-change can be observed in other natural stones like corundum, spinel, and garnet, requiring careful examination for accurate identification. Color -change gemstones exhibit alterations in body color when subjected to different lighting conditions. This phenomenon, known as the alexandrite effect, is most notably observed in the rare alexandrite variety of chrysoberyl. Alexandrite, a prime example, appears red in incandescent light and green in daylight 20XX 39

40. 20XX presentation title 40 Dispersion is an optical property in many gemstones that contributes to color. White light refracts at varying degrees upon entering and leaving a gemstone, creating prismatic colors. Higher degrees of dispersion produce flashes of colored light, known as "fire." The degree of dispersion correlates with refractive index, measured by the difference at the B and G Fraunhofer wavelengths. Diamond has a high refractive index but modest dispersion. Prismatic colors are most noticeable in colorless gems but can still be seen in colored stones like demantoid, garnet, and sphene. Gemstone Coloration due to Interference: Gemstone coloration can arise not only from chemical composition but also from optical effects. One such effect involves the interference between rays reflected from a gemstone's surface layers. This interference generates complementary colors, akin to selective absorption. Alternatively, if the rays are in phase at another wavelength, the reflected color is intensified. This light interference effect significantly contributes to the coloration of gemstones like opal, labradorite, and moonstone. Gemstone Coloration due to Dispersion:

41. 20XX presentation title 41 Gemstone Coloration due to Color-centers: Gemstones get their unique colors from defects in their crystal lattices called color centers . These can be induced by natural or artificial irradiation, resulting in ‘electron’ or 'hole' color centers . Examples include fluorite, quartz, and certain diamonds. Fancy colored diamonds may result from natural irradiation, while zircon colors may stem from impurity atoms. Yellow Cape series diamonds get their color from nitrogen replacing carbon, while rare diamonds like the Dresden Green have a uniform green color due to natural radiation damage. Pink, mauve, and brown diamonds' colors are attributed to plastic deformation, while blue diamonds acquire their color from boron atoms replacing carbon.

42. 20XX presentation title 42 Lustre of a gemstone is the optical effect created by the reflectivity of the stone’s surface. Lustre is directly related to the refractive index of gem material, and although the lustre of some gemstones is visible in the rough, its full potential is usually revealed only when the stone is polished. Because gemstones cover a wide range of refractive indices from 1.43 to 3.32, they also exhibit different degrees of lustre . In recent years, an instrument called a reflectance meter has made it possible to provide a comparative measurement of a stone’s lustre and to use this as a means of identification Optical Properties: Lustre

43. 20XX presentation title 43 Lustre refers to surface reflectivity while sheen results from light rays reflecting beneath a gemstone's surface. There are different types of sheen:- Chatoyancy: creates a band of light caused by reflection from parallel groups of fibers or channels within the stone. Tiger’s-eye displays this effect, with the brightest chatoyant 'line' found in cymophane, a variety of chrysoberyl. Asterism: produces a 'star' effect seen in rubies and sapphires due to fine parallel fibers or crystals intersecting at 60°. Iridescence: presents a play of rainbow-colored light caused by thin layers beneath the gemstone's surface. Labradorescence , seen in labradorite and spectrolite , and adularescence , observed in moonstone, are specific forms of iridescence. Optical Properties: Sheen Asterism in a Ruby Chatoyancy sheen effect

44. Reflection & Refraction Effect of Color on Gemstone Transparency: Color plays a significant role in determining the transparency of a gemstone. Darker colored stones allow less light to pass through, while thicker stones result in greater light loss. Transparent allochromatic gem minerals are difficult to identify based on color alone. Opaque gemstones with distinctive color and surface patterning are more easily recognizable than transparent ones. 20XX 44 Reflection of light is a phenomenon where light waves encounter a surface and bounce back. When light strikes an object or a boundary between two media, a portion of the light is thrown back into the same medium it came from. Refraction of light is the bending or change in direction that occurs when light passes from one medium into another with a different optical density. The speed of light changes as it moves through different substances, causing the light rays to alter their path. The refractive index (RI) is the most important factor when identifying gemstones. The RI of most gemstones is a constant that can be measured accurately to two decimal places, making it easy to distinguish between gems with very little difference in their RI. Refractive index is a numerical index that describes the relationship between the angle of incidence in air and the angle of refraction in the material.  

45. 20XX 45 The Refractometer Critical Angle: Minimum angle for total internal reflection to occur, when light passes from higher to lower refractive index medium. Total Internal Reflection: Light within a medium strikes another medium boundary at angle greater than critical angle, causing total reflection into original medium instead of refraction into second medium .   T he instrument used to measure refractive index (RI). A refractometer measures the extent to which light is bent when it moves from air into a sample. The refractometer has five main components: a rear window, hinged cover, hemicylinder, viewing lens, and scale. The rear window lets light into the device and may have a polarizer. The hinged cover allows you to place the gemstone on the flat side of the hemicylinder. The hemicylinder is a glass tube that has two chambers, one for the gemstone and another for a liquid with a known refractive index. The viewing lens lets you see the shadow of the gemstone on the scale, which shows refractive index values for different colors or wavelengths of light. You read the scale by looking at where the shadow line falls on it. A schematic of a refractometer

46. 20XX presentation title 46 The refractometer works by the use of a glass hemicylinder inside that has a flat surface extending into the body of the refractometer . When light is introduced into the back of the unit, it travel through the glass hemicylinder and up to the gemstone, where the stone is in optical contact with the glass by use of a refractive index liquid. This liquid keeps air from between the stone and the glass hemicylinder and allows light to travel at the same speed through the glass, gets refracted by the gemstone, and then back through the glass hemicylinder to the viewing lens. The amount of slowing down or bending of the light that the gemstone does to the light beam, causes a light and dark area joined by a thin green line as shown below. This green line is the refractive index reading of the gemstone. Working of a Refractometer

47. The lustre , reflectivity or reflectance of a gemstone can be described qualitatively as adamantine, vitreous, resinous, etc. However, it can also be measured in absolute terms as the ratio between the intensity of the reflected ray and that of the incident ray: The degree of luster or reflectivity of a gem (assuming a ‘perfect’ polish) is due mainly to its refractive index but is modified by other factors such as its molecular structure and transparency. 20XX 47 Fresnel’s Reflectivity Equation: The Reflectance Meter: Principle: The principle of reflectivity came into use due to the need for fast identification methods for gemstones with RI over the limits of a standard refractometer. Parts of a Reflectance Meter: Light source: Solid-state IR LEDs Detector: Sealed silicon photodiode. Sensory Slot: Here, Gemstone is placed. Meter: Displays the Reflectivity of the gemstone. Light Shield: Placed over the gemstone to cut-off stray light. Toggle Switch: Used to move between lower & Upper Scale of R.Is. Battery: Usually, a 9V battery. Hanneman ‘Jeweler’s Eye’ reflectance meter Sketch of Jeweller's Eye

48. 20XX presentation title 48 Working of a Reflectance Meter: Center a clean, polished facet of a gem over the 1/32" light sensor hole. Use the provided light shield to cover the gem. Press the red button to activate the Jeweler’s Eye. The needle points to the gemstone based on reflectivity. Ensure the gem is of sufficient size and has a table facet of at least 1/32". Additional scales are available for less common gems on the case. The device is portable, operates on a single 9-volt battery (included), and comes with a carrying case, accessory kit, and recalibration tool. Circuit Diagram of “Jeweller's Eye”

49. Double Refraction in Crystals: Some materials like glass, amber, and cubic crystal system gemstones have one refractive index, leading to a single refracted ray. However, crystalline materials (gemstones) from various crystal systems possess two refractive indices, split into two rays, polarized at right angles, known as double refraction or birefringence . The two polarized rays in birefringent materials travel at different speeds through the crystal and undergo different amounts of refraction. Gemstones with high double refraction, like zircon, exhibit a noticeable doubling of the image of back facet edges when viewed through the main facet using a hand lens. Understanding the degree of double refraction and the specific values of each refractive index aids gemologists in identifying gemstones. This optical property provides a unique characteristic that contributes to the overall assessment and recognition of gemstone types. Unpolarized incident light (vibrating in all directions) is split into two plane polarized rays on entering a doubly refracting materia 20XX 49

50. Refers to the process of transforming unpolarized light waves, which vibrate in all directions perpendicular to their travel path, into polarized light which vibrates in single planes. In a doubly refracting material, such as certain gemstones, unpolarized light passing through emerges as two separate polarized rays. 20XX 50 Polarization Pleochroism An optical phenomenon observed in certain colored gemstones that are doubly refracting. When light enters these stones, it splits into two separate rays polarized at right angles. In pleochroic gemstones, these rays may emerge with differing shades or colors due to differential selective absorption by each ray . If two colors /shades are produced, the stone is termed dichroic, while trichroic stones exhibit three colors /shades. Pleochroism serves as a valuable tool in identifying anisotropic minerals and can enhance the aesthetic appeal of certain gemstones Polarization & Pleochroism

51. 20XX presentation title 51 The Polariscope: A polariscope is an optical tool that uses polarized light to analyze stress distribution in transparent materials. It helps evaluate structural integrity during materials testing and quality control. The polarized light microscope consists of a light source, a polarizer, a sample, an analyzer, a rotating stage, and an observation point/viewer. The light source provides a stable beam of light, the polarizer produces polarized light, the sample exhibits stress patterns, the analyzer controls light intensity, the rotating stage rotates the sample, and the observation point/viewer allows the observer to view the sample.

52. 20XX presentation title 52 Working of a Polariscope: Principle: The interaction of polarized light with the stressed sample creates interference patterns, revealing information about the internal stresses within the material. Adjusting the orientation of the polarizer and analyzer helps in visualizing different aspects of the stress patterns. To observe a gemstone, place the polarizer and analyzer in crossed position, and turn on the light source. Slowly turn the stone while observing it through the analyzer. There are four possible outcomes: Stone appears dark throughout rotation. Stone is isotropic with single refractive index. Stone blinks 4 times, appearing light and dark, which means it's anisotropic with double refractive index. Stone is a microcrystalline or cryptocrystalline aggregate, showing anomalous double refraction (ADR) and is isotropic (single refractive).a a

53. 20XX presentation title 53 The Dichroscope A dichroscope is an optical instrument used in gemmology to analyze a gemstone's colors when viewed from different crystallographic axes, helping gemmologists identify pleochroism. Principle: The dichroscope relies on the differential absorption of light by a gemstone’s crystal structure. Different crystallographic axes absorb light of different wavelengths, resulting in color variations when viewed through the dichroscope. Construction: It typically consists of two calcite prisms or polarizing filters that are joined together. These prisms separate the incoming light into two rays, allowing the gemstone’s pleochroic colors to be observed separately. Two Calcite Dichroscopes Construction Sketch of a dichroscope

54. Luminescence Luminescence refers to the emission of light radiation by certain materials when they absorb energy but do not reach the point of incandescence or burning. The luminescent effect involves the excitation of atoms within the material. The surplus energy causes electrons to move from their stable orbits (ground state) to higher energy levels (excited state). When these electrons return to their stable orbits, they release the surplus energy in the form of electromagnetic radiation, often in the visible spectrum. 20XX presentation title 54

55. Gemstone Luminescence Luminescence is the phenomenon that shows itself as a "glowing" of a gemstone. This is caused by absorption of energy and the releasing of surplus of this energy in small amounts. The sources of energy are usually ultraviolet light, X-ray light, and even visible light. When energy comes from light, it is referred to as  photoluminescence . In gemology we are usually only concerned with the following types of luminescence: Fluorescence Phosphorescence Triboluminescence Tenebrescence (not technically a luminescence) Cathodoluminescence Thermoluminescence The causes of luminescence are varied but are mostly due to impurities ("activators") or due to defects in the crystal lattice. In general, the presence of iron inside the gemstone kills or suppresses luminescence. Photoluminescence & Stokes’ Law: Photoluminescence involves the emission of visible light in response to excitation by electromagnetic radiation, such as visible light, UV radiation, or X-rays. Stokes’ Law specifies that the resulting luminescence always has a longer wavelength than that of the original excitation energy. Photoluminescence is a key feature for gemmologists, aiding in the identification of gemstones. 20XX 55

56. 20XX presentation title 56 Phosphorescence: is a type of luminescence where there is a discernible delay between the absorption of energy and the emission of visible light. The afterglow effect is observable when the excitation source is switched off . It occurs due to the random movement of electrons between their normal and higher energy level orbits. The delayed release of surplus energy distinguishes phosphorescence from fluorescence. Fluorescence: is a type of luminescence where the emission of visible light occurs immediately upon exposure to an excitation source . The luminescent effect ceases as soon as the excitation source is turned off. The movement of electrons between energy levels happens promptly and in a random fashion. Fluorescence is characterized by its immediate response to excitation. T riboluminescence: is the emission of light from Some gemstones, like diamonds, when subjected to pressure or abrasion. It's different from other types of luminescence because it's not caused by light, but by electric charges, which is why it's also called electroluminescence. This effect is often seen when diamonds are cut, producing a red or blue glow. Cathodoluminescence: Materials may display fluorescence when bombarded with electrons in a vacuum , often used for research and analysis. Thermoluminescence: T he ability of certain gemstones to retain the energy they acquire from electromagnetic radiation, and then release it again when heated . This effect is also called thermophosphorescence.

57. 20XX 57 Tenebrescence is a unique property in some minerals and phosphors that causes them to darken in response to radiation and reversibly bleach on exposure to a different wavelength. It is not technically a luminescence , but an unstable color caused by low energy artificial irradiation from the UV light source. A tenebrescent stone requires an external energy source (light) to exhibit its colour, while luminescence is a release of "stored" energy. Examples include hackmanite, sodalite, tugtupite, spodumene, and chameleon diamonds.   Chameleon diamonds are olive-coloured diamonds that temporarily change colour when stored in darkness or gently heated, similar to reversible photochromism. Hackmanite is transparent when extracted but adopts a purple shade after sun exposure, a change that is also reversible.

58. 20XX 58 Gemstone Fluorescence: Ultraviolet light (UV) is the most used excitation source. We cannot see UV light as it sits just below the visible light spectrum (400nm- 700nm) at 10-400nm. UV light enables us to see fluorescence because a gem material will absorb this radiation source and then emit light that is lower in energy and therefore visible to the eye.It has to do with electrons. When electrons are excited by a source of radiation, they jump to a higher energy level around the nucleus of the atom. The excited electron remains in this excited state for a short period of time until it falls back to its original ground state. As the electron returns to its ground state, it emits energy either as heat or as visible light (fluorescence). Using UV Light to Test Gemstones   UV light testing uses two types of light: long wave (LWUV) with a wavelength of 365nm and short wave (SWUV) with a wavelength of 254nm. Equipment ranges from UV keyrings to UV cabinets. When testing gemstones, use caution with SWUV as it can be more dangerous than LWUV and always wear protective UV goggles or ensure your UV cabinet has a filtered eyepiece to protect your eyes from damage. Synthetic Verneuil S apphire, Scapolite, Natural S apphire, Topaz & Citrine Under S-UV Under L-UV

59. 20XX presentation title 59 Fluorescent reactions of some gemstones:

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65. Spectroscopic Techniques in Gemmology In gemstones, color often originates from the presence of 8 transition elements, either as trace impurities or integral components of the gem's chemical composition. In either case, these elements selectively absorb certain wavelengths of light, contributing to the gem's distinct color . A spectroscope is used to analyze the absorption spectrum of a gem, spreading its light into spectral colors and revealing dark lines or bands where specific wavelengths are absorbed. Absorption and Emission Spectra: A spectroscope disperses light into its spectral colors. This process reveals dark lines or bands that make up the absorption spectrum and help to identify absorbed wavelengths in the gemstone. Even unpolished specimens can be positively identified by the characteristic absorption features of transition elements. It is worth noting that different gemstone species with the same transition element can exhibit distinct absorption positions, which enhances the accuracy of identification. In some cases, gemstones exhibit fluorescence , which means they emit light at specific wavelengths when stimulated by incident light. The resulting view through a spectroscope reveals emission lines , forming the emission spectrum . Ruby & Red spinel are notable examples of gemstones that exhibit this phenomenon. They display emission lines at the red end of the spectrum caused by chromium. Red spinel's emission lines are often described as "organ pipes." Observing emission lines is optimal when the specimen is illuminated with blue-filtered light. Spectroscopy   is the field of study that measures and interprets the  electromagnetic spectra  that result from the  interaction  between EMR & matter as a function of the wavelength or  frequency  of the radiation. In simpler terms, spectroscopy is the precise study of  color  as generalized from  visible light  to all bands of the  electromagnetic spectrum. 20XX presentation title 65

66. Types of Spectroscope: Diffraction grating spectroscope The diffraction grating spectroscope is based on the principle of  diffraction . Maybe the best-known brand is OPL, which is produced in the UK by Colin Winter. Light enters through a narrow slit and is then diffracted by a thin film of diffraction grating material. This produces a linear spectrum image with a generally larger view of the red part than a prism spectroscope. These spectroscopes do not have a built-in scale. In gemology, we make use of two different types of spectroscopes, each with its own characteristics. Diffraction grating Spectroscope Prism Spectrscope 20XX 66 Diffraction grating spectra : Without scale With scale in nm a) b) Basic Schematic

67. 20XX presentation title 67 Prism spectroscope The prism spectroscope is based on  dispersion . The light enters through a narrow slit (some models allow you to adjust the width of the slit) and is then dispersed through a series of prisms. Some models have an attachment with a built-in scale. These models are generally more expensive than their diffraction type cousins. Because prism spectroscopes are based on dispersion, the blue area of the spectrum is more spread out and the red parts are more condensed than the diffraction grating types. Prism Spectra : Without scale and with scale in nm . Basic Schematic

68. To use a spectroscope, it is recommended to begin by testing it against various light sources to identify absorption bands. Proper use of the instrument and lighting is crucial to obtain accurate spectra of gemstones. The most common technique is reflecting light off the gemstone at a 45-degree angle. To avoid false readings, use a black, non-reflective surface underneath the stone. Another technique is holding the gemstone and light source in one hand to view it in transmitted light. Experience can eliminate the need for a spectroscope stand. 20XX presentation title 68 Using a Spectroscope:

69. 20XX 69 A selection of principal gemstone spectra as seen using a prism spectroscope

70. Certain gemstones, such as apatite, YAG (yttrium aluminum garnet), colored strontium titanate, and some cubic zirconium oxide (CZ), exhibit a 'fine line' spectrum. This spectrum consists of thin absorption lines distributed across the spectrum, caused by the presence of rare earth elements like neodymium and praseodymium. While zircons may also show a similar spectrum due to trace uranium, the absorption lines in their spectrum are more accurately described as bands. Identification of Synthetic Gems: Man-made gems that owe their color to rare earth elements display a distinct fine line spectrum. This spectrum is notably weaker in natural gems like apatite. A strong fine line spectrum is a positive indication of a synthetic gem. Unlike transition elements, rare earth elements produce unique patterns of fine lines irrespective of the host crystal. 20XX presentation title 70 The upper spectrum is produced by the rare earth Erbium and can be seen in pink CZ and in pink rare earth garnets (YAG). The lower spectrum is caused by dysprosium in yellow/green rare earth garnets Fine Line Spectra in Gemstones:

71. 20XX presentation title 71 Fraunhofer, a Bavarian scientist, detailed the solar spectrum, revealing fine lines known as Fraunhofer lines. Gemmologists often use the Fraunhofer B and G lines for measuring gem dispersion. The B line is at 686.7 nm in the red , and the G line is at 430.8 nm in the blue . These lines serve as standard wavelengths for dispersion measurement in gemmology. Fraunhofer Lines For example, when testing a gemstone, if you observe absorption lines in the blue region at 450, 460 and 470 nanometers (nm), it indicates an iron-caused visible light spectrum.  The conclusion is that the gem is a natural sapphire. Fraunhofer’s drawings of the solar spectrum

72. X-Ray Diffraction Studies: X-ray diffraction is a scientific technique that analyzes the crystallographic structure of a material. It measures the diffraction patterns generated when X-rays interact with the crystal lattice. The crystal structure can be determined by measuring the angles and intensities of the diffracted X-rays. X-ray diffraction is a crucial tool in gemology. It is used to identify minerals and gemstones based on their crystal structures, characterize their internal arrangement of atoms, detect changes in their structure, and ensure the quality of gem materials. It is also employed in gemmological research and mineralogical studies to explore new gem deposits and identify minerals in various geological contexts. 20XX 72

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74. 20XX presentation title 74 It is also possible to differentiate based on main components, i.e. whether a ruby or sapphire is really corundum (Al2 O3 ) or just colored glass (SiO2 ). The spectrum shows the corundum ruby and sapphire, as well as an emerald with clearly different signals of the main components Al and Si. The contents of detectable elements range from about 10 ppm to a percentage range. XRF-XRD patterns

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76. 20XX presentation title 76 This graph shows a comparison spectrum of a natural and an artificial ruby. Traces of additional elements such as gallium and bismuth are detectable in natural gemstones, which are not present in synthetic gemstones. These are spectrally purer, so they contain hardly any additional trace elements.

77. 20XX presentation title 77 Artificial gemstones can be distinguished from natural gemstones based on their coloring elements. In this spectrum, the blue color of the synthetic sapphire has been created by adding cobalt oxide. However, no cobalt oxide is present in the natural gemstone. Instead, the color originates from iron oxide.

78. 20XX presentation title 78 Pearls can be cultured, but a saltwater pearl is much more valuable than a freshwater pearl due to the effort required to cultivate it, and it looks very similar. Determining whether it is a fresh or salt water pearl can be done with an XRF instrument by analyzing the manganese content, because the matrix in both kinds is calcium carbonate (CaCO3 ) and thus identical. If a pearl is cultured in fresh water, more manganese is stored in it than in a saltwater pearl. Fresh water contains a relatively high amount of manganese (5 ppb) compared to salt water

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