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 1ST 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:
Al2SiO5. 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 : Al2SiO5
 ANDALUSITE : Al2SiO5
 SILLIMANITE : Al2SiO5
OTHER ISOLATED TETRAHEDRA
 STAUROLITE Fe2Al9SiO23(OH)
 TOPAZ : Al2SiO4(F,OH)2
 Andalucite,kyanite,and sillimanite are
reconstructive polymorphs.

5. Kyanite, Andalusite, Sillimanite: all Al2SiO5, 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,GRE
Y,YELLOW
WHITE,GREY,YEL
LOW,GREEN
PINK,VIOLET,YEL
LOW,GREEN
LUSTER VITREOUSTO
PEARLY
VITREOUSTO
SUBADMANTINE
VITREOUS
HARDNESS 4.5-5&6.5-7 6.5-7.5 6.5-7.5
FRACTURE SPLINTERY UNEVEN UNEVEN
CLEAVAGE PERFECTON
100&GOOD ON
010
PERFECTON 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 COLOURLESSTO
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° MORETHAN 80°

8. ANDALUSITESITE
KYANITESILLIMANITE
DISCRIPTION
rDESCRIPTION
of
the Aluminosilicate Group:
Al2SiO5
oup:
Al2SiO5

9.  Kyanite, Andalusite, Sillimanite, Staurolite, Topaz, all these
minerals having Neso-silicate structure.
 Silicate mineral containing independent (insular) SiO4
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 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
RarelyVisible In Outcrop scale

15. PARAGENESIS:
In high-grade
metamorphic
schist, gneisses,
and hornfels ; more
rarely in
pegmatites. Also as
a detrital mineral.

16. STRUCTURE OFANDALUSITE
 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