Muscovite

DETAILS ABOUT MUSCOVITE AND BIOTITE

1. MUSCOVITE AND BIOTITE A GEOLOGY STUDY Submitted by ; Debasis prusty R egd no : 18mscegs07 Submitted to : Dr. Jitendra Kumar Patnaik

2. CONTENT INTRODUCTION ORIGIN OF MICA CHEMICAL FORMULA PHYSICAL PROPERTIES OPTICAL PROPERTIES XRD OF MINERAL STRUCTURE OF MICA CHEMISTRY OF MICA OCCURRENCE USES

3. Introduction The Name Muscovite derives from its use in Windows as Muscovy glass . Muscovy being an old Russian Provenance . Muscovite is the most common member of the mica group. It typically occur as Massively crystalline material in flaky grain. The Mineral biotite named after J.B Biot 1774-1862 a French scientist who conducted detailed studies of mica. Mica , any of a group of hydrous  Potassium, Aluminum silicate Mineral. It is a type of  Phyllosilicate, exhibiting a two-dimensional sheet or layer structure. Among the Principal rock-forming minerals, Micas are found in all three major rock varieties—Igneous , Sedimentary , and Metamorphic .

4. Origin of M ica Micas may originate as the result of diverse Processes under Several different Conditions . Their Occurrences, include crystallization from consolidating  Magmas deposition  by fluids derived from or directly associated with magmatic activities , deposition  by fluids circulating during both contact and regional metamorphism, A nd F ormation as the result of alteration Processes—Perhaps even those caused by Weathering—that involve Minerals such as Feldspars. Some aspect of their chemical composition may serve as geothermometers or geobarometers.

5. Chemical Formula Formula : KAl 2 (AlSi 3 O 10 )( OH) 2 (Muscovite) K( Mg , Fe) 3 (AlSi 3 O 10 )(OH) 2 (Biotite) Elements listed: Al,   H,   K,   O,   Si Common Impurities: Cr,Li,Fe,V,Mn,Na,Cs,Rb,Ca,Mg,H 2 O

6. PROPERTIES MUSCOVITE BIOTITE Habit Usually tabulated , Foliated Micaceous - Platy texture Colour white Dark brown, Greenish brown Luster silky /pearly Vitreous - Pearly Streak white gray Hardness 2-2.5 2.5-3 Fracture Micaceous Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern. Cleavage Present 1set Perfect [001] Basal, perfect Specific gravity 2.8 2.7 to 3.4 Crystalize system Monoclinic Monoclinic Chemical composition KAl 2 (AlSi 3 O 10 ) (OH) 2 K( Mg , Fe) 3 (AlSi 3 O 10 )(OH) 2

7. Optical Properties PROPERTIES MUSCOVITE BIOTITE Type: Biaxial Negative Biaxial Negative 2V: Angle Of Inclination Measured: 30° to 47° Measured; 0 to 32 Surface Relief Moderate  moderate Dispersion: r > v weak r < v  weak (Fe rich) Pleochroism: Weak Strong Birefringence  0.036-0.049  0.028-0.08 Extinction -  straight, mottled straight, mottled RI 1.552-1.618 1.53-1.696 Interference Colour   3rd order 2nd-3rd order

8. Structure of Mica PROPERTIES MUSCOVITE BIOTITE Crystal System Monoclinic Monoclinic Point Group 2/m 2/m Space Group C2/c C2/m Z(No of Formula Units Per cell) 4 2 Unit Cell Parameters in Angstrom a 5.19 5.33 b 9.04 9.31 c 20.08 10.16 Diagnostic Properties – The Perfect Cleavage Produce flexible and elastic growth identifies muscovite as a Mica. There are eight major  diagnostic properties  of minerals: crystal habit, luster, hardness, cleavage, fracture, color, streak, and specific gravity. Micas Show a Peculiar O ptical Property Known as Birds eye Structure .(Special Feature)

9. XRD A scattering of X-rays by the atoms of a crystal that produces an interference effect so that the diffraction pattern gives information on the structure of the crystal or the identity of a crystalline substance. One of these methods, X-ray powder diffraction ( XRD ), is an instrumental technique that is  used  to identify minerals, as well as other crystalline materials.

10. Muscovite XRD

11. Biotite XRD

12. Structure Of Muscovite Micas have Sheet structures whose basic units consist of two polymerized sheets of silica (SiO 4 )  tetrahedrons . Two such sheets are  Joining  with the vertices of their tetrahedrons pointing toward each other; the sheets are cross-linked with Cation— for example, aluminum in muscovite—and hydroxyl pairs complete the coordination of these cations. Thus, the cross-linked double layer is bound firmly, has the bases of silica tetrahedrons on both of its outer sides, and has a negative charge. The charge is balanced by singly charged large cations—for example, potassium in muscovite—that join the cross-linked double layers to form the complete structure. The differences among mica species depend upon differences in the  X  and  Y  cations.

13. Chemistry Of Muscovite Muscovite may range considerably in composition as a result of atomic Substitutions. Some Na is generally present replacing k; Replacement is greater the higher the temperature of formation , A nd the sodium content of muscovite may thus be a useful geological thermometer. (When Na content exceeds K content the mineral called paragonite) . Aluminium in Six Coordination May be Partly replaced by Mg and Fe+2 or less commonly by Cr3+ giving a bright green Colour . The ratio of Si:Al in four coordination ranges from 3:1 to about 7:1 high Silica Content Muscovite is Generally referred to by the Varity name Phengite , Some F may be Present Replacing OH.

14. Chemistry Of Muscovite Although the micas are generally considered to be Monoclinic , (pseudo hexagonal), there also are Hexagonal, Orthorhombic, and  Triclinic forms generally referred to as polytype. The polytypes are based on the sequences and number of layers of the basic structure in the unit cell and the symmetry thus produced. Most biotite are 1M and most Muscovites are 2M; however, more than one polytype is commonly present in individual specimens. This feature cannot, however, be determined macroscopically; polytypes are distinguished by relatively Complicated techniques such as those employing X-rays.

15. Muscovite occurrence Muscovite is particularly common in metamorphic gneisses, schists, and phyllites. In fine-grained foliated rocks, such as phyllites, the muscovite occurs as microscopic grains (sericite) that give these rocks their silky lusters. It also occurs in some granitic rocks and is common in complex granitic pegmatite and within miarolitic druses, which are late-magmatic, crystal-lined cavities in igneous rocks. Much of the muscovite in igneous rocks is thought to have been formed late during, or immediately after, consolidation of the parent magma . Muscovite is relatively resistant to weathering and thus occurs in many soils developed over muscovite-bearing rocks and also in the clastic sediments and sedimentary rocks derived from them.

16. Biotite Occurrences The common rock-forming micas are distributed widely. Biotite  occurs in many igneous rocks (e.g., granites and granodiorites), is common in many  pegmatite masses , and  constitutes one of the chief components of many metamorphic rocks (e.g., gneisses, schists, and hornfelses ). It alters rather easily during  Chemical weathering  and thus is rare in sediments and sedimentary rocks. During chemical weathering, biotite tends to lose its elasticity and become decolorized to silvery gray flakes. In a fairly common intermediate stage, weathered biotite is golden yellow, has a bronzy luster, and may be mistaken by inexperienced observers as flakes of gold.

17. Uses Of Muscovite and Biotite The  Ground mica is used as a pigment extender in paint. It helps keep pigment in suspension; reduces chalking, shrinking, and shearing of the finished surface;  mica is used as an inert filler and mold release agent in the manufacture of molded rubber products such as tires and roofing. The sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, lightweight, reflective, refractive and resilient. Biotite has a small number of commercial uses. Ground mica is used as a filler and extender in paints, as an additive to drilling muds, as an inert filler and mold-release agent in rubber products etc.

18. References A TEXT BOOK OF GEOLOGY MINERALOGY BY DEXTER PERKINS PRINCIPLES OF ENGINEERING GEOLOGY BY K.M. BANGAR WWW.WEBMINERAL.COM WWW.GEOLOGY.COM WWW.MINDAT.COM

19. Thanks