Mica are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in many granites, pegmatites, and schists.

1. DEPARTMENT OF APPLIED GEOLOGY
SCHOOL OF ENGINEERING AND TECHNOLOGY
DR. HARISINGH GOUR VISHWAVIDYALAYA (A CENTRAL UNIVERSITY)
SEMINAR PRESENTATION ON: MICA FAMILY
GUIDED BY PRESENTED BY
PROF A. K. SHANDILYA GOURAV RAJAK
M. TECH 1ST SEM

2. CONTENTS
• Introduction
• Atomic structure
• Chemistry
• Some important minerals
• Use of Mica
• Mica Distribution in India
• Bibliography

3. INTRODUCTION
Mica is the name given to a group of phyllosilicate minerals that have silicon and oxygen as
their two major components.
• Has Si:O ratio of 2:5 (4:10).
• Has Perfect Basal cleavage parallel to {001}
• Hardness is 3
• Monoclinic.
• Mica also has a brilliant shine that glitters and sparkles. In fact, the name mica is believed
to have come from the Latin word mica which means to shine. Mica is responsible for the
flashes of light in composite rocks such as granite, gneiss, and slate.

4. ATOMIC STRUCTURE
• Mica minerals belong to phyllosilicates.
• The SiO4 tetrahedron is linked by three
corners to the neighbouring tetrahedron
forming a sheet.
• Each SiO4 tetrahedron has three shared and
one free oxygen.
• The atomic structure consist of two
tetrahedral sheet and one octahedral
sheet(2:1)
• Two of these sheet of linked tetrahedral
are placed together with the vertices of the
tetrahedral pointing inwards.

5. • The general formula – XY2-3Z4 O10(OH,F)2
where, X=K, Ca(Na in case of paragonite)
Y = Al, Li, Mg , Fe and Z = Si and Al.
• In mica minerals the Si : Al ratio found to be 3:1.

6. Dioctahedral Micas Trioctahedral Micas
Dioctahedral refers to having two of
the three available octahedrally
coordinated positions occupied .
Trioctahedral refers to having all three
available octahedrally coordinated
positions occupied.
Aluminium ion occurs as a cation in
octahedral co-ordination
Magnesium and Ferrous ion occurs as a
cation in octahedral co-ordination
Example:- Muscovite, Paragonite Example:- Biotite, Phlogopite, Annite

7. Color Colorless
Forms Flakes Massive.
Cleavage Perfect parallel to {001}.
Lustre Vitreous.
Streak White.
Twinning Present with twin axis
being [310].
Hardness 2.5-3.
Specific Gravity 2.77-2.88.
Transparency Transparent.
Tenacity Elastic.
MUSCOVITE (POTASSIUM MICA)
 Named after the Muscovy principality of thirteenth century Russia , which produced
muscovite for use in window panes.
 KAl2(AlSi3O10 )(OH)2

8. OPTICAL PROPERTIES MUSCOVITE
Color Colorless
Pleochroism None
Relief Moderate positive relief.
Optic Orientation X^c = 1 to 4º, Y^a =1 to 3º Z= b
Refractive Index and
Birefringence
nα = 1.552-1.576, nβ = 1.582-1.615, nγ =
1.587-1.618.
Polarisation color Third order colors.
Extinction Straight
Optic Axial Ang. 2V= 30-47o , Biaxial (-).
Muscovite Under PPL
and XPL
Occurrence:-
Muscovite is a common mineral found in igneous,
metamorphic, and sedimentary rocks. In igneous rocks
it is a common constituent of granitic pegmatite,
granite, granodionte, aplite, and related felsic rocks. It
is somewhat less common in felsic volcanic rocks

9. PHYSICAL PROPERTIES BIOTITE
Color Black or dark brown.
Forms Flaky, Massive.
Cleavage Perfect parallel to {001}.
Lustre Splendent.
Streak White.
Twinning Present with twin axis being
[310].
Hardness 2.5-3.
Specific Gravity 2.7-3.3.
Transparency Transparent to Translucent.
Tenacity: Brittle to flexible, elastic.
BIOTITE (Magnesium, Iron MICA)
•K(Mg,Fe)3AlSi3O10(F,OH)2.

10. OPTICAL
PROPERTIES
BIOTITE
Color Colorless
Pleochroism Strong; X = gray-yellow, yellow-brown,
orange-brown; Y = Z = dark brown, dark
green, dark red-brown.
Relief Moderate positive relief.
Optic Orientation Y = b; X^c = 0-3o; Z^c =0-9o
Refractive Index and
Birefringence
α= 1.565-1.625, β=1.605-1.696 γ=1.605-
1.696
Polarisation color:- Masked by its deep intrinsic color
Extinction Straight
Optic Axial Angle 2V(meas)= 0-25o , Biaxial (-).
Occurence:-
Members of the biotite group are found in a wide variety of igneous and
metamorphic rocks.
Biotite under PPL and XPL

11. PHLOGOPITE
Chemical Composition: KMg3AlSi3O10(F,OH)2.
PHYSICAL PROPERTIES PHLOGOPITE
Color Brownish red, dark brown,
yellowish brown, green
Forms Six-sided prismatic crystals
Cleavage Perfect parallel to {001}
Lustre Splendent
Streak White
Twinning On composition plane {001},
twin axis [310].
Hardness 2-3
Specific Gravity 2.7-2.85
Transparency Transparent to Translucent
Tenacity: Brittle to flexible, elastic

12. OPTICAL PROPERTIES PHLOGOPITE
Color Pale brown, nearly colourless
Pleochroism Weak with pale colours; α= yellow, βand γ deep yellow or
brownish red. X = yellow; Y = Z = brownish red,
green,yellow
Relief Low to moderate.
Optic Orientation Y=b; Z^a = 0-5o
Refractive Index and Birefringence α= 1.530-1.590 β=1.557-1.637 γ=1.558-1.637.
Polarisation color Third order colors.
Extinction Straight
Optic Axial Angle 2V = 0-15o , Biaxial (-).
Occurence:-
• Found in metamorphosed impure magnesian limestone
• Common constituent of kimberlites, and is a minor constituent of ultramafic rocks

13. PHYSICAL
PROPERTIES
PARAGONITE
NaAl2(AlSi3O10)(OH)2.
LEPIDOLITE
K(Li,Al)3(Si,Al)4O10(OH,F)2
ANNITE
KFe3AlSi3O10(F,OH)2
Color Pale yellow or pale green Rose red. Black, Brown
Forms Foliated, massive or
disseminated scales.
Flat Sheets, aggregates of fine
grains
Flat Sheets.
Cleavage Perfect parallel to {001} Perfect parallel to {001} Perfect parallel to {001}
Lustre Pearly Sub-Vitreous, Resinous, Greasy,
Pearly.
Submetallic to vitreous; pearly on
cleavage surfaces.
Streak White White white
Twinning On composition plane {001},
twin axis [310].
Rare. On composition plane {001}, twin
axis [310].
Hardness 2.5-3 2.5 – 3.5 2.5 - 3
Specific Gravity 2.78 2.8 -2.9 3.3
Transparency Transparent to Translucent Transparent to Translucent Transparent to Translucent
Some Other Minerals From Mica Group

14. OPTICAL
PROPERTIES
PARAGONITE LEPIDOLITE ANNITE
Color Colourless Colorless to pale pink in thin
section.
Brown, black
Pleochroism None X = almost colorless; Y = Z =
pink, pale violet
X = brown; Y = Z = dark brown.
Relief Moderate positive relief. Moderate positive relief. Moderate
Optic Orientation Y ^a; Z = b; X ^ c =50. Y=b; X^ a =900-870 Z^ a =0- 7° Y = b
Refractive Index and
Birefringence
α = 1.564-1.580 β = 1.594-
1.609 ° γ= 1.600-1.609
α = 1.525- 1.548 β = 1.551-
1.585 γ= 1.554-1.587
α= 1.624 o β = 1.672 ° ,γ=
1.672
Polarisation color Third order colors. Third order colors. Masked By Color.
Extinction Straight Straight Straight
Optic Axial Angle 2V = 0- 40° , Biaxial(-) 2V = 00-580. Biaxial(-) 2V= 0- 5o , Biaxial(-)

15. PARAGONITE LEPIDOLITE ANNITE
MARGARITE ZINWALDITE

16. PHYSICAL PROPERTIES ZINWALDITE
KLiFeAl(AlSi3)O10(OH,F)2
MARGARITE
CaAl2(Al2Si2O10)(OH)2
Color Violet, pale yellow or brown in color. Grayish, pale pink, yellow, or green
Forms Scaly aggregates; Platy
Cleavage Perfect parallel to {001} Perfect parallel to {001}
Lustre Pearly Pearly.
Streak White White
Twinning On composition plane {001}, twin axis
[310].
On composition plane {001}, twin axis [310].
Hardness 2.5-4 3.5- 4.5
Specific Gravity 2.90-3.02 2.99- 3.08
Transparency Transparent to Translucent Transparent to Translucent
Some Other Minerals From Mica Group

17. OPTICAL PROPERTIES ZINWALDITE MARGARITE
Color Colourless to light brown Colorless.
Pleochroism Distinct; X = colorless to yellow-brown; Y
=gray-brown; Z = colorless to gray-brown.
Absent.
Relief Low to Moderate Moderate.
Optic Orientation Y=b; X^a = 88-90o Z^c =0-2o Y^a= 6-80 ; X^c =11-130 , Z=b
Refractive Index and
Birefringence
α= 1.535-1.558 β=1.570-1.589 γ=1.572-
1.590.
α= 1.630-1.638, β=1.642-1.64 γ=1.644-
1.650
Polarisation color:- Low order colors. Low order colors.
Extinction Straight Straight
Optic Axial Angle 2V = 0- 40°, Biaxial(-) 2V = 400-670, Biaxial(-).

18. Uses of Mica
• Pigment extender in paints and also helps to lighten the tone of colored pigments
• Sparkly look, it is ideal for toothpaste and cosmetics.
• Excellent thermal resistance, it may be utilized as an insulator in a variety of electrical
devices.( Capacitors, Transistors, Insulators, etc).
• Mica (Glauconite) is used as a fertilizer to provide K.
• As a constituent of drilling mud used when drilling for oil and gas.
Insulator Paint and Pigment Oil and Gas Exploration Rubber Tyres

19. Mica Distribution in India
1. Andhra Pradesh:
Andhra Pradesh is the largest mica producing state of India. In Andhra Pradesh. Nellore,
Vishakhapatnam, West Godavari, and Krishna.
2. Rajasthan:
Second largest producer. Bhilwara district located in this belt is the most imported producer of
Mica.
3. Jharkhand:
Third largest producer. Kodarma (largest reserve of mica in the world), Giridih, and Domchanch
are the chief collecting centers (located in this belt) where Mica is processed.
Apart from this Munger in Bihar also have sufficient mica deposits.
The main centres of mica production in this belt are Kodarma, Dhorhakola, Domchanch, Dhab,
Gawan, Tisri, Chakai and Chakapathal.
4. Karnataka:
Mica deposits occur in Mysuru and Hasan districts of Karanataka
5. Tamil Nadu:
In Tamil Nadu, Coimbatore, Tiruchirapalli, Madurai and Kanniyakumari districts
6. Kerala:
In Kerala, Mica deposits are found in Alleppey district.
7. Maharashtra:
Ratnagiri in Maharashtra has rich mica deposits.
8. West Bengal:
Purulia and Bankura in West Bengal are known for mica deposits.

20. Bilbliography
Books:
• Nesse William D. Introduction to Mineralogy, Oxford University press.
• Perkins Dexter, Mineralogy, Third Edition, Pearson Education Limited
• Rutley's: Elements of Mineralogy, 26th Edition, 1976
• Deer, W.A.; Howie, R.A.; Zussman, J. (1966). An Introduction to the Rock Forming
Minerals. London: Longman. p. 218.
Links and URLs
• https://www.mindat.org/min-3090.html
• https://en.wikipedia.org/wiki/Paragonite
• https://www.mindat.org/min-2380.html
• https://geology.com/minerals/lepidolite.shtml
• microckscopic.ro/minerals/silicates/phyllosilicates/biotite-thin-section/
• https://en.wikipedia.org/wiki/Biotite
• https://lotusarise.com/mica-limestone-reserves-in-india-upsc/

21. THANKYOU