Aluminosilicate group of minerals( mineralogy)

mineralogy aluminosilicates

1. DR. HARI SINGH G0UR vishwavidyalaya , SAGAR, m.p (A CENTRal university ) SEMINAR PRESENTATION ON ALUMINOSILICATE GUIDED BY : PROF. R.K TRIVEDI Dr. G. C. GAUTAM DEPARTMENT OF APPLIED GEOLOGY SUBMITTED BY: ASHUTOSH CHAKRA REG NO-Y18251007 SERIAL NO-07 SESSION-2018-19 M.TECH 1 ST SEMESTER

2. CONTENT INTRODUCTION POLYMORPHS PHASE DIAGRAM PHYSICAL AND OPTICAL PROPERTIES DESCRIPTION OF POLYMORPHS 1-Andalusite 2-Sillimanite 3-Kyanite 0THER MINERALS 1-Topaz 2-Staurolite USES GEOGRAPHICAL DISTRIBUTION

3. INTRODUCTION Aluminosilicate  minerals are composed of aluminium , silicon, and oxygen. They are a major component of kaolin and other clay minerals. Aluminosilicate minerals have the chemical formula: Al 2 SiO 5 . It has density of 2.8 to 2.9g/cm Aluminosilicate minerals are common in aluminous metamorphic rocks (meta- shales and mud stone ) and some times found in aluminous igneous rocks .

4. POLYMORPHS KYANITE : Al 2 SiO 5 ANDALUSITE : Al 2 SiO 5 SILLIMANITE : Al 2 SiO 5 OTHER ISOLATED TETRAHEDRA STAUROLITE Fe 2 Al 9 SiO 23 (OH) TOPAZ : Al 2 SiO 4 (F,OH) 2 Andalucite,kyanite,and sillimanite are reconstructive polymorphs.

5. Kyanite, Andalusite, Sillimanite: all Al 2 SiO 5 , different crystal structures - polymorphs. Andalusite - low P & T; Kyanite - high P; Sillimanite - high T. PHASE DIAGRAM

6. PHYSICAL PROPERTIES PROPERTIES &CRYSTAL DATA KYANITE SILLIMANITE ANDALUSITE CRYSTAL SYSTEM TRICLINIC ORTHORHOMBIC ORTHORHOMBIC COLOUR BLUE,WHITE,GREY,YELLOW WHITE,GREY,YELLOW,GREEN PINK,VIOLET,YELLOW,GREEN LUSTER VITREOUS TO PEARLY VITREOUS TO SUBADMANTINE VITREOUS HARDNESS 4.5-5&6.5-7 6.5-7.5 6.5-7.5 FRACTURE SPLINTERY UNEVEN UNEVEN CLEAVAGE PERFECT ON 100&GOOD ON 010 PERFECT ON 010 GOOD ON 110&POOR ON 100 HABBIT BLADED FIBROUS MASSIVE SP.GRAVITY HIGH LOW LOW STREAK WHITE WHITE WHITE TRANSPARENCY TRANSPARENT TO TRANSLUSCENT TRANSPARENT TO TRANSLUSCENT TRANSPARENT TO NEARLY OPAQUE

7. OPTICAL PROPERTIES PROPERTIES KYANITE SILLIMANITE ANDALUSITE COLOUR COLOURLESS TO LIGHT BLUE COLOURLESS COLOURLESS IN PPL & PINK IN XPL PLEOCHROISM WEAK PLEOCHROIC NON PLEOCHROIC WEAKLY PLEOCHROIC OPTIC SIGN BIAXIAL(-) BIAXIAL(+) BIAXIAL(-) EXTINCTION INCLINED PARALLEL PARALLEL RELIEF HIGH (+) HIGH(+) MODERATELY HIGH (+) 2V ANGLE 78-83° 20-30° MORE THAN 80°

8. ANDALUSITE SITE KYANITE SILLIMANITE DISCRIPTION r DESCRIPTION of the Aluminosilicate Group: Al 2 SiO 5 oup : Al 2 SiO 5

9. Kyanite, Andalusite, Sillimanite, Staurolite, Topaz, all these minerals having Neso -silicate structure. Silicate mineral containing independent (insular) SiO 4 4- tetrahedral are known as neso -silicate, orthosilicates . . STRUCTURE OF POLYMORPHS

10. STRUCTURE OF KYANITE Kyanite has a structure in which the oxygen atoms are arranged in a slightly distorted close-packed cubic array. Chain of Al-O octahedra and these chain are linked together by the remaining si , Al and oxygen ions. Si being coordinated by 4-O ions and Al by 6-oxygen ions.

11. Kyanite Examples

12. PARAGENESIS In gneisses, schists , included pegmatites , and quartz veins, from moderately high-pressure regional metamorphism of principally pelitic rocks; detrital in sedimentary rocks . DISTRIBUTION India is the largest kyanite producer in the world . Singhbhum (Jharkhand )

13. STRUCTURE OF SILLIMANITE The stucture of sillimanite consist of chains edge sharing Al octahedra is parellel to c axis that are linked laterallly Al and Si. The lateral linkage between chain made by chain of alternating Al and Si tetrahedra . The Al is half in octahedra coordination and half in tetrahedra coordiination

14. Sillimanite In Outcrop Rarely Visible In Outcrop scale

15. PARAGENESIS:

16. STRUCTURE OF ANDALUSITE Andalusite has graphic inclusion. In andalusite edge-sharing chains of Al octahedra extended parellel to the c axis and are bonded lateraly through pairs of Al in distorded 5 fold cordination and single Si in tetrhedron . Characterized by square prism and hardness.

17. Andalusite In Outcrop

18. PARAGENESIS A result of contact metamorphism of argillaceous sediments, also in regionally metamorphosed schists . Rare in granites and pegmatites , which however afford the largest crystals. Detrital in some sandstones. Occur in contact aureoles of igneous intrusions in Al rich rocks. DISTRIBUTION Deposit of andalusite schist is near Canso, Nova Scotia. The Goat Mountain deposit in Idaho(U.S).

19. USES Although the three minerals that comprise the sillimanite group have different properties, they are all used primarily as raw materials in the manufacture of heat-resistant refractory ceramics. Today it is estimated that 70% of the kyanite output is used in refractories: 55% for smelting and processing of ferrous metals, 10% for nonferrous metals, and 5% for glassmaking and ceramics. All the sillimanite minerals convert to mullite (about 88%)and silica (about 12%) when heated to temperatures ranging from1,250°C to 1,500°C.

20. GEOGRAPHIC DISTRIBUTION OF ALUMINOSILICATE Jharkhand: Singbhum , Hazaribagh districts Rajasthan: Ajmer, Dungarpur and Udaipur Punjab: Patiala district Maharastra : Bhandara district Gujrat : Idar district Andhra Pradesh: Nellore,Chikmagalur district. Karnataka: Hassan district West Bengal: Darjeeling, Purulia , Bankura district. Madhya Pradesh & Chhattisgarh: Rewa & Bastar

21. Kyanite, andalusite , sillimanite , and synthetic mullite production

22. REFERENCE INTRODUCTION TO MINERALOGY- WILLIAM D. NESSE MINERALOGY- BY – DEXTER PERKINS INTRODUCTION TO ROCK-FORMING MINERALS-J.ZUSSMAN Wikipedia.org

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