topaz

topaz

1. SEMINAR ON TOPAZ

2. CONTENTS INTRODUCTION PHYSICAL PROPERTIES OF TOPAZ OPTICAL PROPERTIES OF TOPAZ TYPES OF TOPAZ PARAGENESIS OF TOPAZ WORLD OCCURENCE INDIAN OCCURENCE USES OF TOPAZ CONCLUSION REFERENCE

3. INTRODUCTION Topaz is an aluminium silicate containing fluorine and has a chemical formula of Al2 SIO4(F,OH)2. Topaz is a well-known mineral, occurring in large and beautifully shaped and coloured crystals. It naturally occurs in many colours, but rarely in pink, purple, and deep blue.

4. PHYSICAL PROPERTIES OF TOPAZ Color of the Topaz is Colorless, White, Yellow, Pink, Blue, Green, Grey Streak of the topaz is Colorless luster is vitreous Diaphaneity Transparent to translucent cleavage It has perfect basal cleavage Hardness of the topaz is 8 Specific gravity is 3.4-3.6 Distinguishing characteristics are Hardness and prismatic crystals and its orthorhombic Crystal system Habit is Usually well-formed prisms.

5. Optical Properties Of Topaz Degree of transparency is Transparent and Luster possess Vitreous . Refractive index - Colorless, Blue and Green;1.607-1.617.Yellow,Brown&Red;1.629-1.637. Optic character- Biaxial positive weak to distinct. Pleochroism - Blue : Colorless light blue Yellow:Brownish yellow & orange yellow Brown:Yellow-brown & brown Red and Pink : Light Red & Yellowish Red to yellow Green : Blue - Green & Light Green Optic character - Biaxial positive weak to distinct Pleochroism - Blue : Colorless light blue Yellow : Brownish Yellow & orange yellow Brown :Yellow-brown & brown Red and Pink : Light Red &Yellowish Red to yellow

6. CONT .... Dispersion- 0.14 X-ray Fluorescence - Blue &Colorless stones glow a Greenish or V iolet –Blue color. The color emitted by Yellow, Brown &Pink stones varies from Brownish Yellow to Orange. Ultraviolet Florescence - Colorless - none to pale Yellow Red : Weak Brownish Yellow Yellow : Weak Orange Yellow Blue : None Brown.

7. PARAGENESIS OF TOPAZ Topaz is formed through pneumatolytic processes in which hot gases play an essential role. It forms late in the cooling of a silica-rich igneous mass. Topaz is typically found as a component of pegmatite dikes where crystals reach huge sizes. Additionally , it occurs in the cavities of gneisses, schists and highly acid rocks like rhyolite. Topaz is a common component in gem gravels because of its hardness and relative durability.

8. DIFFERENT TYPES OF TOPAZS Topaz comes in many different colours including orange, yellow, brown, light blue to deep sky blue, pink, colourless, white, light purple, greenish-blue and green.

9. SIMILAR GEMSTONES Since topaz occurs in a great range of colors, it may resemble many other gemstones: Orange-brown and Imperial Topaz - Zircon , Chrysoberyl , Golden Beryl , Sapphire . Pink Topaz - Morganite , Tourmaline , Rose Quartz , Spinel Yellow Topaz - Chrysoberyl , Heliodor , Zircon , Yellow Sapphire Blue Topaz - Aquamarine , Zircon , Spinel White Topaz - Diamond , Zircon

10. The high relief ,weak birefringence, positive optic sign, prismatic form and moderate 2v are characteristic of topaz. It differs from andalusite in having a smaller 2v and in having y parallel to z. DISTINGUISHING FEATURES

11. Where TOPAZ comes from Some of the places Topaz comes from Brazil ,USSR, Utah, California in USA & Sri Lanka.

12. WORLD OCCURENCE Ouro Preto in Brazil is known for highly prized orange – yellow to brown topaz recovered from altered pegmatite's Gem gravels in Sri Lanka and Myanmar(Burma) are important sources of topaz. Topaz is also found in Australia, Japan, Pakistan, and Mexico, United States.

13. INDIAN OCCURENCE Many localities in Orissa are rich in colourless topaz which can be enhanced to blue by irradiation and heating . Rolled pebbles are found in the beds of Mahanadi river in Orissa . Topaz bearing pegmatite's have been noticed in few localities in Singhbhum dist.. in Bihar. Topaz is also found in Karur-Kangyam belt of Tamil Nadu.

14. CONT..... Aruvikkara gravel deposits in Kerala have yielded small quantity of Topaz. Kyanite-bearing rocks of Mogra and Girola areas in Bhandara dist.. Maharashtra possess topaz.

15. USES OF TOPAZ Topaz is a popular gemstone. The most common use for topaz is as a gemstone in jewellery. Topaz is a hard gemstone, but this hardness also increases it’s tendency to break. Because of this, topaz is typically used for jewellery that will not be knocked around or come in contact with hard surfaces. Industrially also topaz is useful and a component in blade making industry.

16. TOPAZS IN JEWELLERY

17. CONCLUSIONS Topaz is usually found in igneous rocks: granitic, pegmatites, cavities in rhyolites, and hydrothermal replacement deposits. Colorless crystals are common usual colour are yellow ,orange, red, pink , blue and green . Topaz has highly perfect cleavage. since Topaz hardness is 8, it takes super fine polish . Topaz is not only used as gem stone but also finds place in industry.

18. REFERENCES GEMS AND GEM INDUSTRY IN INDIA BY R.V.KARANTH (2000) PG.NO-303&304. http : // www. ehow.com / ... tant – uses –topaz-gem.... http : // www. Webcrawler.com / ...

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