Transcript UNIT-II MINERALOGY

UNIT-II
MINERALOGY
MINERALOGY
• A mineral is naturally occurring homogeneous inorganic substance
having distinctive physical properties and a more or less definite
chemical composition.
• Minerals are to a large extent the units which make up the rocks of
the earths crust or the outer shell.
MODE OF FORMATION OF MINERALS
• Three kinds of formation of minerals in nature
I.
1.
Formed from magma
2.
Secondary process
3.
Metamorphism
Directly formed from deposition of molten magma - feldspar, quartz,
pyroxenes, amphiboles, micas
II.
Due to weathering, precipitation, deposition (secondary process) –
calcite, dolomite, bauxite, coal, petroleum
III.
Formed under the influence of high temperatures and pressures with
and without the active involvement of chemically active solution
(metamorphism)- Garnets, chlorite, graphite
CRYSTALLOGRAPHY
• Great majority of minerals when the conditions of formations are
favorable, occur in definite and characteristic geometric forms
known as crystals.
• Crystal-Greek word “Krystallos” meaning clear ice.
• The study of crystals is called as crystallography..
• “Crystals are bodies bounded by surfaces usually flat, arranged on
a definite plan which is an expression of an orderly internal
arrangement of the atoms”.
CRYSTALLOGRAPHIC ARRANGEMENT
SYMMETRY
• All crystals show by the arrangement of their faces a definite
symmetry which enables one to group them into different classes
• Types of symmetry
– Plane of symmetry
– Axis of symmetry
– Centre of symmetry
SYMMETRY
1.PLANE OF SYMMETRY
A plane of symmetry divides a
crystal into two similar and
similarly placed halves
2.Axis of symmetry
If a crystal on being rotated comes to occupy
the same position in space more than once in
a complete turn the axis about which the
rotation has taken Is called as axis of
symmetry
3.Centre of symmetry
A crystal is said to have centre of symmetry if an imaginary line can be passed
from any point on its surface through its centre and a similar point can be found
on the line at an equal distance beyond the centre
PHYSICAL PROPERTIES
1. Colour
2. Lustre
3. Structure
4. Hardness
5. Cleavage
6. Fracture
7. Specific gravity
8. Tenacity
9. Odour and taste
Colour
very useful in identifying mineral in spite of the fact that colour is constant
in most of the minerals and commonly colour is due to stain or impurities in
the minerals.
Lustre
Appearance of a fresh surface of a mineral in a ordinary reflected light
Metallic- galena
Glassy-vitreous
Pearly-talc
Structure
Term used to denote the shape and form of minerals.
1. Columnar
2. Bladed
3. Fibrous
4. Radiated
5. Lamellar
6. granular
Hardness
Resistance a mineral offers to abrasion or scratching and is measure
relative to a standard scale of ten minerals known as Moh’s scale of
hardness
Cleavage
Tendency of many crystallized minerals to break or split in certain parallel
directions yielding more or less smooth surfaces known as cleavage
planes.
May be perfect and imperfect
Fracture
Appearance of the broken surface of the mineral.
Specific gravity
Specific gravity of a mineral is the ratio of its weight to the weight of an
equal volume of water.
Tenacity
The resistance which the mineral offers to breaking, crushing, bending
or tearing-in short its cohesiveness is known as tenacity
Ex Brittle, sec tile, malleable, flexible and ductile
Taste
A few minerals which are soluble in water have more or less
characteristic tastes
Acid, alkaline, astringent, bitter, cooling, pungent, saline
ISOMORPHISM
• Peculiar natural phenomenon
• Minerals appear to be mixtures of two different
minerals from chemical composition.
• This type of formation is called as isomorphism
• Examples: Feldspar, pyroxene, amphiboles and garnets
ROCK FORMING MINERALS
• Silicate ranks first in the earths crust for rock forming minerals.
• SiO4 tetrahedron ins the fundamental unit of all silicate minerals.
STRUCTURE OF SILICATES:
1.
Nesosilicates - SiO4 occurs as Independent unit E.g. garnet.
2.
Sorosilicate - SiO4 occurs as pairs unit E.g. garnet.
3.
Inosilicate - SiO4 occurs as chains along one direction or single chain
silicates e.g. pyroxenes
4.
Cyclosilicates - SiO4 occurs as ring form as 3 or 4 units called as ring
silicates e.g beryl
5.
Phyllosilicates - SiO4 occurs as sheets; called as sheet silicates. E.g mica,
chlorite
6.
Tectosilicates - SiO4 occurs as three dimensional frame work e.g quartz,
feldspar
MINERAL GROUP OR FAMILIES
• Some silicate minerals have similar atomic structure and
chemical composition. Such set of minerals are called as
groups or families.
Examples of some important groups of silicate minerals
1. Feldspar group
2. Pyroxene group
3. Amphibole group
4. Garnet group
IMPORTANT DETAILS OF ROCK FORMING MINERAL
I. FELDSPARS
• Most abundant of all the silicate minerals.
• The name refers to a group and not a single mineral
• Make up about half the rocks of earths crust
• Form monoclinic and triclinic crystals and are aluminous silicates of K,
Na or Ca.
• Three common molecules
– Orthoclase
-
KAlSi3O3
– Albite
-
NaAlSi308
– Anorthite -
CaAlSi3O8
CRYSTAL SYSTEM : MONOCLINIC
Any mineral that falls under the
following specifications belongs to
the monoclinic crystal system.
 Three axes, all of them are
unequal in length. Two of them
are at right angles to each
other, while the third is lies at
an angle other than 90°.
CHEMICAL COMPOSITION-FELDSPAR
In chemical constitution, felspars are chiefly Alumino-silicates of sodium,
potassium and calcium with the following general formula : WZ4 O8
where W=Na ,K, Ca and Ba and Z= Si and Al .
The Si : Al shows a variation of 3:1 to 1:1 .
Some examples of chemical composition of felspar minerals are : KAlSi3O8
– NaAlSi3O8 – CaAl2Si2O8
Occurs in isomorphous series
ATOMIC STRUCTURE-FELDSPAR
1. At atomic level ,the felspars shows a continuous three-dimensional
network type of structure in which SiO4 tetrahedra are linked at all the
corners, each oxygen ion being shared by two adjacent tetrahedral.
2. The SiO4 tetrahedra is accompanied by AlO4 tetrahedra so that the
feldspar are complex three dimensional framework of the above two
types of tetrahedra.
3. The resulting network is negatively charged and these negative
charges are satisfied by the presence of positively charged K, Na, Ca
and Ba.
4.
The felspar group of minerals crystallize only in two crystallographic
systems Monoclinic and Triclinic.
CRYSTALLIZATION
The feldsdpar group of minerals crystallize only in two crystallographic systems
Monoclinic and Triclinic.
CLASSIFICATION
Chemically felspar fall into two main groups:
The potash felspar
 The soda lime felspar .
Common members of the two groups are Potash felspar :
Orthoclase (KAlSi3O8), Sanidine(KAlSi3O8) and Microline (KAlSi3O8).
Soda – lime feldspar :
These are also called the plagioclase feldspars and consists of an
isomorphous series of six felspar with two components: NAlSi3O8 and Ca Al2
Si2O8 as the end members.
1. Albite
4. Labradorite
2. Oligoclase
5. Bytwonite
3. Andesine
6. Anorthite
The above series is also known as Albite-Anorthite series.
Crystallographically ,felspar fall in two crystal systems .
Monoclinic Feldspars
1. Orthoclase (KAlSi3O8 )
2. Sanidine (KAlSi3O8 )
Triclinic Feldspars
1. Microcline (KAlSi3O8 )
2. Albite – Anorthite series (six minerals)-(six minerals)
PHYSICAL PROPERTIES
In addition to their close relationship in chemical composition ,crystallography and
atomic constitution ,felspar group of minerals exhibit a broad similarity and closeness
in their physical characters as well so that differentiation of one variety from other
requires very thorough, sometimes microscopic examination.
 Light in colour,
 lower specific gravity ,
 have a double cleavage and a hardness varying between 6-6.5.
COMMON TYPE OF MINERALS
1.
Orthoclase 2. Microcline 3. Albite 4. Anorthite
PHYSICAL PROPERTIES-FELDSPAR
Form
Tubular, mineral occurs as uniform thickness
Colour
Generally white, pale grey or pale red
Streak
White or pale body colour
Lustre
Vitreous
Fracture
Even to uneven
Cleavage
Two sets one set is better developed
Hardness
6
Density
Medium, 2.57
Occurrence
weathering
Orthoclase
Crystal system
Monoclinic ; β=63•57•.Crystals commonly occur in prismatic
shape.
Cleavage
Shows cleavage in 2 directions. The one parallel to basal pinacoid
(001) is perfect. The cleavage angle is 90•.
Colour
Various shades of pink and red, such as flesh red, reddish white,
light pink . The transparent variety is called the Adularia .
Luster
Vitreous to semiviterous.
Hardness and specific
gravity
6-6.5 ; 2.56 to 2.58
Composition
KAlSi3O8
Optical
Optically negative (-)
Occurrence
A most common and essential constituent of many igneous rocks
,especially granites .
Economic use
As a ceramic material.
Varieties
1. Adularia-a transparent orthoclase.
2. Sanidinc-a high temperature variety stable above 900•C
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microcline
Crystal system
Triclinic, resembles closely with orthoclase in crystal
habits.
Cleavage
In two directions, the one parallel to basal pinacoid(001) is
perfect.
Colour
Similar to orthoclase. In addition , may occur as a greenish
felspar,when it is called amazonite.
Streak ,hardness and specific
gravity
colorless, 6-6.5,2.54 to 2.57
Composition
KAlSi3O8
Optical
Optically negative (-).
Occurrence
It occurs along with the orthoclase in granites and other
igneous rocks.
Economic use
As a ceramic material and semi-precious stone (amazonite).
Varieties
Anorthoclase (meaning-not orthoclase).It is a triclinic
felspar containing sodium aluminum silicate.
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albite
Crystal system
Triclinic ,it is the first member of the isomorphous
plagioclase series .
Cleavage
Present in 2 directions. the one parallel to basal pinacoid
(001)is perfect.
Colour
Commonly whitish or pinkish white but shows shades of
grey,green and blue.
Streak
Colourless
Luster
Vitreous to pearly.
Hardness and specific gravity
6-6.5 , 2.60-2.62
Composition
Sodium aluminum silicate with NaAlSi3O8 - 100-90 % and
CaAl2Si2O8 -0-10%.
Optical
Optically positive(+).
Occurrence
It is an essential constituent of many igneous rocks such
as granite,syenites,rhyolites and dacites.
Economic use
As a ceramic material.
As an ornamental stone in polished form.
anorthite
Crystal system
Triclinic, it is the last member of the isomorphous plagioclase series.
Cleavage
Present in two directions, the one parallel to basal pinacoid (001)if
perfect .
Colour
Generally white, may also occur in reddish and light grey shades.
Streak
Colourless
Luster
Semi-vitreous.
Composition
CaAl2Si2O8 -100-90%
Optical
Optically positive (+)
Occurrence
An important constituent of many basic types of igneous rocks.
Varieties
Composition of other members of plagioclase felspars has mentioned
above . These maybe broadly considered the varieties of plagioclase
felspars.
II. QUARTZ
•
•
•
•
•
Composition of SiO2
Most abundant material next to felspar
Colourless or white
Many coloured varieties are mainly due to impurities.
Three main varieties
1. Crystalline -Rock crystal, amethyst, rose quartz, milky quartz
2. Crypto-crystalline -Chalcedony, carnclian
3. Amorphous-opal
Mostly used for jewellery and ornamental purposes
QUARTZ
Crystal system
Hexagonal, (rhombohedral). Crystals common ; some
crystals weighing many tones have been reported.
Twinned ,right-handed and left-handed crystals are
common.
Cleavage
Generally absent
Fracture
Conchoidal
Colour
Colourless when pure, quartz also occur in coloured
varieties :red, green , blue and mixture.
Hardness
7
Sp. Gravity
2.65-2.66
Streak
White in coloured varieties
Varieties
It is a very common rock forming mineral and occurs in
numerous varieties . A few common varieties are mentioned
below.
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Polymorphous transformation
Quartz, when heated , transforms into high temperature modifications as follows:
(870•C)
(1470•C)
(1713•C)
Quartz ↔ Tridymite ↔ Cristobalite ↔ melt
The variety named as QUARTZ itself has two polymorphs :
1. Α quartz,
2. β quartz.
Identification of the exact type of quartz (into Αand β) requires thoroug
investigations of the mode of formation of mineral as observed by its place of
occurrence and also type of symmetry.
Right handed and left handed quartz :
 When occurring, quartz may be distinguished into right handed and left handed
types.
Carried out on the basis of recognition of some typical faces such as trigonal,
trapezohedron and dipyramid. These two faces normally occur at the edges of the
prism faces, one above the another. In the left handed quartz ,these faces are located
on the left side of the upper edge of the prism, whereas in the right handed quartz,
these occur on the right upper edge of the crystals. Such a location of these faces in
manifestation of an internal atomic arrangement in the crystal.
• COLOURED VARIETIES :
Common pure quartz is a colourless transparent mineral. Presence of even a trace
of an impurity may give it a characteristic colour and hence a variety . A few
common types of quartz distinguished on their basis are :
1. Amethyst – purple or violet
2. Smoky- dark to light brown, even black
3. Milky- pure white and opaque
4. Rose red – colour is attributed to presence of titanium.
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CRYPTOCRYSTALLINE TYPES :
In many cases, crystalline of pure silica to quartz remains incomplete due to interruption in
the process for one reason to another. Silica occurring in these cryptocrystalline varieties,
although close in composition and physical properties to quartz is named differently. A few
common varieties of cryptocrystalline silica are as follows :
1. Chalcedony – luster ,waxy, commonly translucent, generally massive.
2. Agate – often banded , opaque and massive.
3. Onyx – a regularly banded agate having alternating and evenly paced layers of different
colours.
4. Flint – a dull opaque variety of chalcedony breaking with characteristic conchoidal fracture.
5. Jasper- a dull red, yellow,almost amorphous variety of silica.
OCCURRENCE
Quartz and its varieties occur in all types of rocks ;igneous, sedimentary and metamorphic.
In igneous rocks, quartz makes up bulk of acidic varieties.
In sedimentary rocks quartz makes up sandstones and ortho quartzites.
Loose sands consist mostly of quartz grains.
The metamorphic rocks like gneisses contain good proportion of quartz in some cases.
A metamorphic rock named as (Para) quartzite is entirely made up of quartz.
PIEZOELECTRICITY
Quartz crystals have piezoelectric properties; they develop an electric potential upon
the application of mechanical stress. An early use of this property of quartz crystals
was in phonograph pickups. One of the most common piezoelectric uses of quartz
today is as a crystal oscillator. The quartz clock is a familiar device using the
mineral. The resonant frequency of a quartz crystal oscillator is changed by
mechanically loading it, and this principle is used for very accurate measurements
of very small mass changes in the quartz crystal microbalance and in thin-film
thickness monitors.
Quartz scepters
PHYSICAL PROPERTIES-QUARTZ
Form
Granular or short prismatic
Colour
Black or dark greenish black; pale colour – magnesium rich
pyroxene
Streak
White or pale body
Lustre
Vitreous
Fracture
Uneven
Cleavage
Two sets od prismatic cleavage 87° and 93°
Hardness
5 to 6
Density
Medium
Specific gravity 3.2 to 3.5
III. PYROXENE
• Constitute important group of minerals that are generally
recognized by their stout crystals and their two cleavages
right angles to each other.
• Most pyroxenes are dark coloured
• Ca, Mg and Fe silicate composition
• Varieties
– Monoclinic pyroxene
- Augite
– Orthorhombic pyroxene - Hypersthene
CHEMICAL COMPOSITION
– Composition mainly consists of silicates of calcium, magnesium and
ferrous iron.
– At initial formation magnesium rich varieties
– At later stage iron rich formation
– General formula R2(AlSi)2 where R –divalent calcium, magnesium or
ferrous iron
ATOMIC STRUCTURE
– Single chain silicates
– Have 1:3 ratio of silicon and oxygen
– Mostly crystallize in the form of either orthorhombic or monoclinic
system
MONOCLINIC PYROXENE- AUGITE
AUGITE - DESCRIPTION
• Chemical Formula: (Ca,Na)(Mg,Fe,Al)(Al,Si)2O6
• Augite is an important rock-forming mineral, and large crystals are
fairly common.
• It is the most widespread member of the pyroxene group, and it
frequently alters to many other minerals, including Hornblende.
• Augite usually occurs in dull crystals that are ugly and uninteresting.
• The name Augite is derived from the Greek word augites,
"brightness", in reference to the bright luster this mineral
occasionally exhibits.
OCCURRENCE
• Major rock forming mineral in mafic igneous
rocks, ultramafic rocks and some high grade
metamorphic rocks.
Crystal System : Monoclinic
• Any mineral that falls
under the following
specifications belongs to
the monoclinic crystal
system:
Three axes, all of them
are unequal in length.
Two of them are at right
angles to each other,
while the third is lies at
an angle other than 90°.
AUGITE – PHYSICAL PROPERTIES
• Colour : dark green to black
• Streak : white to gray, augite can be slightly harder than a streak plate so
brittle fragments rather than a powder will sometimes be produced.
• Lustre : vitreous
• Diaphaneity : translucent to opaque
• Cleavage : prismatic
• Hardness : 5.5 – 6
• Specific Gravity : 3.2 - 3.6
• Distinguishing Characteristics : Two cleavage directions almost at right angles,
dark green to black colour
• Chemical Classification : silicate
USES OF AUGITE
• Augite is a dark green to black mineral that is used for
ceramics.
• It contains large amounts of aluminum, iron, and
magnesium and can be found in meteroic stones.
• ceramic glazing, manufacturing aluminum, purifying water.
IV.AMPHIBOLES
Another type
of mineral
AMPHIBOLE MINERALS
Crystallization
ORTHORHOMBIC
Important
MONOCLINIC
Crystals – long, slender, prismatic, sometimes fibrous
Prism angle – 124’
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Amphibole Group – Resemble – Pyroxene Group
CHARACTERISTICS
• HARDNESS: 5 – 6
• SPECIFIC GRAVITY: 3 – 3.5
• Dark in Colour
CHEMICAL COMPOSITION
• Amphibole minerals – Metal silicates – Si : O – 4 : 11
• Ca, Mg, Fe, Mn, Na, K, H – metallic ions
• (OH) ions – F and Cl –
• Chemical Formula – [Si4 O11]2 [OH]2
• Various ions – Al, Mg, Fe, Ca, Na, K, H, F – replaced – giving rise to a variety of Amphibole
minerals
ATOMIC STRUCTURE
• Difference – Amphiboles and Pyroxenes
• Amphiboles – SiO4 tetrahedra – double chains
• Reason – more complex than Pyroxenes – chemical composition
PHYSICAL PROPERTIES
•
•
•
•
•
•
•
Crystallise in only 2 crystal systems
Dark in colour.
Hardness – 5 to 6
Specific Gravity – 2.8 to 3.6
Elongated
Slender
Often fibrous in nature
Orthorhombic Amphiboles
ANTHOPHYLLITE (Mg, Fe)3 [Si4O11]2 [OH]2
CRYSTAL SYSTEM
Orthorhombic – thin, slender fibres
CLEAVAGE
Perfect and Prismatic
COLOR
Grey, brownish or greenish
HARDNESS
5.56 – 6
SP. GRAVITY
2.85 – 3.20
LUSTRE
Vitreous
OPTICAL
Optically (+)
OCCURRENCE
Only in metamorphic rocks
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VARIETIES OF AMPHIBOLES
1. Hornblende
2. Tremolite
3. Actinolite
4. Asbestos
Hornblende is the most common variety
AMPHIBOLE - 1.Hornblende
Hornblende – Description
 Chemical formula : Ca2(Mg,Fe)4Al(Si7Al)O22(OH,F)2
 Any of a subgroup of amphibole minerals that are calciumiron-magnesium-rich and monoclinic in crystal structure.
 Hornblende, occurs widely in metamorphic and igneous
rocks.
 Common hornblende is dark green to black in colour and
usually found in middle-grade metamorphic rocks (formed
under medium conditions of temperature and pressure).
 Such metamorphic rocks with abundant hornblende are
called amphibolite's.
System : Monoclinic
• Block diagram showing the
relationship
between
the
crystallographic axes and the
indicatrix axes.
OPTICAL PROPERTIES
• Colour : distinctly coloured, shades of green, yellow-green, bluegreen and brown
• Composition : exhibits a wide range of compositions.
• Occurrence : common mineral found in a variety of geological
environments, i.e. in igneous, metamorphic and sedimentary rocks
• Alteration : may be altered to biotite, chlorite or other Fe-Mg
silicates
• Distinguishing Features : cleavage and grain shape, inclined
extinction, pleochroism
PHYSICAL PROPERTIES
• Colour : dark green to black.
• Streak : gray to greenish gray
• Lustre : vitreous
• Diaphaneity : translucent to nearly opaque
• Cleavage : good
• Hardness : 5.0 - 6.0
• Specific Gravity : 3.0 - 3.5
USES
• The hornblende mineral is
used in a variety of common
things that we use every day.
• These things include: steel,
soap,
statues.
oil,
buildings,
and
Ca2Mg5 [(Si4O11)]2 [OH]2
CRYSTAL SYSTEM
Monoclinic –long, bladed
CLEAVAGE
Prismatic and Perfect
COLOUR
White to light grey
HARDNESS
5.5 – 6.0
SP. GRAVITY
2.9 – 3.0
LUSTRE
Vitreous
OPTICAL
Optically (-)
OCCURRENCE
Igneous and metamorphic rocks..
(mostly)
Ca2 (Mg, Fe)5 [(Si4O11)]2 [OH]2
CRYSTAL SYSTEM
Monoclinic
CLEAVAGE
Perfect and Prismatic
COLOUR
Green due to ferrous ion
HARDNESS
5.5 – 6.0
SP. GRAVITY
3.1 – 3.3
VARIETY
Asbestos – fibrous form – long and
flexible fibres
V. INTRODUCTION-MICA
• Mica is the name given to a group of
silicate minerals that
have silicon and oxygen as their two
major components.
• The Mica family of minerals includes
several variations based on chemical
composition and characteristics.
 Mica’s are besides feldspars, pyroxenes and amphiboles, very
common rock forming minerals comprising approximately 4
percent of the Earth.
 They have great variation in their Chemical Composition.
 Despite this, mica minerals are easily grouped together
because of their similar atomic structure.
 (Mica’s yield water when heated in a closed test tube.)
DIFFERENT TYPES
The 11 common variations are:
1. Biotite
2. Celadonite
3. Fuchsite
4. Glauconite
5. Lepidolite
6. Margarite
7. Muscovite
8. Phengite (or) Mariposite
9. Phlogopite
10. Sericite
11. Stilpnomelane
The many variations come from the diverse ways it formed. Mica
formations are associated with volcanoes and hydrothermal vents.
GENERAL FORMULA
Chemically, micas can be given the general formula
X2Y4–6 Z8 O20(OH,F)4
in which,
X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;
Z is chiefly Si or Al, but also may include Fe3+ or Ti.
CHARACTERISTICS
• Mica has a brilliant shininess that glitters and sparkles. In fact
the name mica is believed to have come from the Latin word
‘MICARE’ which means “to shine.”
• Mica is responsible for the flashes of light in composite rocks
such as granite, gneiss, and slate.
• The crystal structure is monoclinic with a somewhat
hexagonal crystal shape. These two characteristics are due to
the structure of the atoms that make up the mica group.
PROPERTIES
Name
Content
Color
White, Yellowish, Green, Gray
Streak
Colorless
Luster
Vitreous to Pearly
Transparency
Transparent, Translucent and
Opaque
Crystal System
Monoclinic
Specific Gravity
2.8
Hardness(Mohs)
2.5-3
Cleavage
Perfect
Fracture
Uneven
Uses
Mainly as Insulators in Electronics
Location
Mica is found in many rocks around the world.
Notable deposits are found in India, South
Dakota, Russia and Brazil. Larger deposits are
found in Colorado(USA), Evje(Norway) and Minas
Gerais(Brazil).
BIOTITE
DESCRIPTION OF BIOTITE
• General Formula: K2(Mg,Fe)3 AlSi3O10(OH,O,F2)2
• Biotite is a group of common rock-forming minerals
forming a series between phlogopite and annite. The name
is best used as a field name for dark micas for which the
exact composition has not been determined.
DESCRIPTION OF BIOTITE – CONTD.
• Biotite survives a certain amount of weathering and is found in
soils, sediments and sedimentary rocks. Weathered Biotite
becomes relatively brassy of bronzy in colour and has been
mistaken for gold.
• Its lower density, cleavage, and other properties are soon
apparent to the careful observer. Finally Biotite can form as a
result of hydrothermal processes, especially wall-rock alteration
around ore veins.
OPTICAL PROPERTIES
• Colour: Typically brown, brownish green or reddish brown.
• Occurrence: Common in a wide range of igneous and metamorphic rocks
and may be an important detrital mineral in sediments.
• Cleavage: Perfect cleavage on {001}.
• Twinning: Rarely visible.
• Optic Orientation: Extinction is parallel or nearly parallel, with a maximum
extinction angle of a few degrees. Cleavage traces are length slow.
• Alteration: Alters to chlorite, clay minerals, and/or sericite, iron-titanium
oxides, epidote, calcite, and sulphides
• Distinguishing Features : colour, "birds-eye" extinction, nearly parallel
extinction
BIOTITE - PHYSICAL PROPERTIES
• Colour: black, dark green, dark brown
• Streak: white to gray.
• Lustre: vitreous.
• Diaphaneity: transparent to translucent.
• Cleavage: basal, perfect
• Hardness: 2.5 – 3
• Specific Gravity: 2.7 - 3.3
• Chemical Classification: silicate
BIOTITE - USES
• Biotite has very limited commercial use.
• Biotite particles are sometimes used as a surface treatment in
decorative concrete, plaster and other construction materials.
• It is also used in the potassium-argon method of dating
igneous rocks.
MUSCOVITE
OCCURRENCE
• A common rock forming mineral, muscovite is found in
igneous, metamorphic and detrital sedimentary rocks.
• It is not usually valuable as a mineral specimen but can be
found associated with other valued minerals such as
tourmaline, topaz, beryl, almandine and others.
MINERAL DESCRIPTION
• Chemical formula : KAl2(AlSi3O10)(F,OH)2
• MUSCOVITE was once commonly used for windows.
• The Russian mica mines that produced it gave muscovite its name (it
was once widely known as "Muscovy glass").
• Muscovite is a high-aluminium member of the mica family of minerals,
all known for the property of perfect basal cleavage; cleavage layers
can be easily peeled off into very thin sheets which are quite durable
and are not easily destroyed by erosion.
•
Muscovite sheets have high heat and electrical insulating properties
and are used to make electrical components.
OPTICAL PROPERTIES
• Colour : colourless
• Composition : highly variable
• Form : found as micaceous flakes or tablets with irregular outlines
• Twinning : rare
• Optic Orientation : parallel extinction, cleavage traces are length slow
• Alteration : not generally altered
• Distinguishing Features : colourless, parallel extinction, "birds-eye" extinction
• Bird's
of
eye
maple,
extinction
or
exhibited
bird's
by
eye
extinction,
minerals
of
the
is
a
mica
specific
group
type
under
cross polarized light (sometimes called the optical analyser). It gives the
mineral a pebbly appearance as it passes into extinction.
SYSTEM: MONOCLINIC
• Block diagram showing the
relationship between the
crystallographic axes and
the indicatrix axes.
MUSCOVITE - PHYSICAL PROPERTIES
• Colour : colourless, yellow, brown,
green, red
• Streak : white
• Lustre : vitreous
• Diaphaneity : transparent to translucent
• Cleavage : perfect
• Hardness : 2.5 – 3
• Specific Gravity : 2.8 - 2.9
• Chemical Classification : silicate
MUSCOVITE – USES
• Muscovite has a high resistance to
heat
and,
split
into
thin
transparent sheets, it has been
used
as
windows
on
high-
temperature furnaces and ovens.
• It is an insulator and was used in
the past to make circuit boards.
• Historically, it was used as an early
window glass.
CALCITE
CALCITE - DESCRIPTION
• Calcite is a rock-forming mineral with a chemical formula of
CaCO3.
• It is extremely common and found throughout the world
in sedimentary, metamorphic and igneous rocks.
• Calcite is the principal constituent of limestone and marble.
• These rocks are extremely common and make up a
significant portion of Earth's crust.
• They serve as one of the largest carbon repositories on our
planet.
CALCITE - DESCRIPTION – CONTD.
• The properties of calcite make it one of the most widely used
minerals.
• It is used as a construction material, abrasive, agricultural soil
treatment, construction aggregate, pigment, pharmaceutical and
more.
•
It
has
more
uses
than
almost
any
other
mineral.
CRYSTAL SYSTEM
•
The true rhombohedral unit cell,
which is the acute rhombohedra,
and the cleavage rhombohedron
setup.
• The true unit cell includes 2
CaCO3 with calcium ions at the
corners of the rhombohedron and
CO3 groups.
• Each of which consists of a carbon
ion at the centre of a planar group of
oxygen atoms whose centres define
an equilateral triangle.
CALCITE – PHYSICAL PROPERTY
• Mineral class : Carbonates - Calcite group.
• Cleavage : Perfect rhomboedric in three planes, subconchoidal
fracture.
• Hardness : 3
• Density : 2.7
• Colour : usually colourless, but nuances in blue, yellow, green,
red, violet, even black and opaque.
• Streak : White to greyish.
• Lustre : Vitreous to pearly or dull.
USES OF CALCITE IN CONSTRUCTION
• The construction industry is the primary consumer of calcite
in the form of limestone and marble.
•
These rocks have been used as dimension stones and in
mortar for thousands of years.
• Limestone blocks were the primary construction material
used in many of the pyramids of Egypt and Latin America.
• Today, rough and polished limestone and marble are still an
important material used in prestige architecture.
USES OF CALCITE IN CONSTRUCTION – CONTD.
• Modern construction uses calcite in the form of limestone and
marble to produce cement and concrete.
• These materials are easily mixed, transported and placed in the
form of a slurry that will harden into a durable construction
material.
• Concrete is used to make buildings, highways, bridges, walls .
OTHER USES OF CALCITE
• In a powdered form, calcite often has an extremely white colour.
• Powdered calcite is often used as a white pigment or "whiting".
• Some of the earliest paints were made with calcite. It is a primary
ingredient in whitewash and it is used as an inert colouring
ingredient of paint.
• It is softer than the stone, porcelain and plastic surfaces found in
kitchens and bathrooms but more durable than dried food and
other debris that people want to remove .
• This is a non-flammable dust that is sprayed onto the walls and
roofs of underground coal mines to reduce the amount of coal dust.
GYPSUM (CaSO4.2H2O)
• Gypsum- a soft sulphate mineral composed of calcium
sulphate di hydrate.
• Gypsum was known in Old English as spærstān, "spear
stone", referring to its crystalline projections.
• Dehydrated gypsum is popularly known as “plaster of
Paris”.
• Gypsum crystals contain anion water and hydrogen
bonding.
PROPERTIES
• Category
• Colour
• Cleavage
• Mohs scale
• Lustre
• Specific
gravity
• Solubility
-Sulphate minerals
-White, colorless. May be pink,
brown, red due to impurities.
-Perfect on 010 distinct on 100
-1.5-2
-Vitreous to silky, pearly or waxy.
-2.31 to 2.33
-Hot, dilute Hcl
GYPSUM CRYSTALS
APPLICATIONS
•
•
•
•
Used as cement blocks in building.
An ancient mortar used in building construction.
Binder in fast-dry tennis courts.
Fertilizer and soil conditioner.
CLAY
• Clay- a fine grained soil.
• Distinguished from other soil by size.
• Formed by gradual weathering of rocks.
• Absorb or lose water depending on humidity changes.
• Due to absorption of water, specific gravity of clay is
variable.
• Divided into kaolinite, illite, vermiculite, smectite and
chlorite.
PRODUCTION
USES
• Used in pottery, decorative and construction products.
• Macaws use clay licks for survival.
• Can soothe an upset stomach.
• Primary ingredient in building techniques.
• Kaolin clay – used as anti-diarrheal medicines.
• Removal of heavy metals from waste water.
PROPERTIES
QUARTZ
FELSPAR
GROUP
MUSCOVI BIOTITE
TE
MICA
GYPSUM
CRYSTAL
SYSTEM
Hexagona Monoclinic
l
and
Triclinic
Monoclini Monoclinic Monoclinic Category
c
of sulphate
COLOUR
Colourles
s when
pure; red,
green,
blue
Grey,
green,
blue, pink
and white
White to
Colourles
s
Greenish
to brown
or black;
even
yellow
White,
White,
yellowish, colourless
green, grey
HARDNESS
7
6 – 6.5
2 – 2.5
2.5 - 3
2.5 - 3
1.5 - 2
SPECIFIC
GRAVITY
2.65 –
2.66
2.54 – 2.57
2.76 - 3
2.7 – 3.1
2.8
2.31 – 2.33
CLEAVAGE
Generally
absent
Perfect
Highly
perfect
basal
cleavage
Highly
perfect
basal
cleavage
Perfect
Perfect
LUSTRE
Vitreous
Vitreous
Vitreous
Vitreous
Vitreous
Vitreous
PROPERTIES AMPHIBOLE
MINERALS
CALCITE
CRYSTAL
SYSTEM
Monoclinic
Crystalline, granular,
rhombohedra
COLOUR
White to light grey White or colourless;
also grey, yellow &
green
HARDNESS
5.5 – 6
3
SPECIFIC
GRAVITY
2.9 - 3
2.71
CLEAVAGE
Perfect
Perfect with 74’
LUSTRE
Vitreous
Vitreous