Minerals found in the crust are in solid form where as in intrior they are in liquid form98% of
the crust consist of eight elements
1.oxygen 2. Silicon 3. Aluminium 4. Iron. 5. Calcium 6. Sodium 7. Potassium 8. Magnes
the rest is constituted by titanium, hydrogen, phosphorous, manganese, sulphur carbon, nickel
& other elements
Many elements found in combination with other elements. These substances are called minerals
Mineral: naturally occuring inorganic substance having an orderly atomic structure and a definite
chemical composition and physical properties.
It is composed of two or three minerals /single element ex. S,Cu, Ag,Au, Graphite.
There are at least 2000 minerals in the crust. There are at least six mineral groups which form
rocks in the crust.
The basic source of all minerals is the hot magma in the interior of the earth. Coal, petroleum and
natural gas are organic minerals
PHYSICAL CHARACTERISTICS OF MINERALS
(I) EXTERNAL CRYSTAL FORM:Internal arrangement of molecules-cube,
octahedrons,hexagonal, prisms.
(II) CLEAVAGE:
CHAPTER-5 MINERALS AND ROCKS
Figure 7 PRISM
Figure 8 CUBE Figure
OCTAHEDRONS
Figure 9
HEXAGONAL
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Tendency to break in given direcations producing relatively
plane surfaces, it may any direction
FRACTURE: Conchoidal fracture
Obsidian
Conchoidal fracture is a curved breakage that resembles the concentric
ripples of a mussel shell. It often occurs in amorphous or fine-grained
minerals such as flint, opal or obsidian, but may also occur in crystalline
minerals such as quartz. Sub conchoidal fracture is similar to conchoidal
fracture, but not as curved. (Note that obsidian is an igneous rock, not a
mineral, but it does illustrate conchoidal fracture well.)
Earthy fracture
Limonite
Earthy fracture is reminiscent of freshly broken soil. It is frequently seen in
relatively soft, loosely bound minerals, such as limonite, kaolinite and
aluminite.
Hackly fracture
Native copper
Hackly fracture (also known as jagged fracture) is jagged, sharp and
uneven. It occurs when metals are torn, and so is often encountered in
native metals such as copper and silver.
Splintery fracture
Chrysotile
Splintery fracture comprises sharp elongated points. It is particularly
seen in fibrous minerals such as chrysotile, but may also occur in nonfibrous
minerals such as kyanite.
Uneven fracture
Magnetite
Uneven fracture is self descriptive. It occurs in a wide range of
minerals including arsenopyrite, pyrite and magnetite.The crystal
breaks inan irregular manner not along the planes
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LUSTURE : Adamantine lustre
Cut diamonds
Adamantine minerals possess a superlative lustre, which is most notably seen
in diamond.[1] Such minerals are transparent or translucent, and have a high
refractive index (of 1.9 or more).[2] Minerals with a true adamantine lustre are
uncommon, with examples being cerussite and zircon.[2]
Minerals with a lesser (but still relatively high) degree of luster are referred to as subadamantine,
with some examples being garnet and corundum
Dull lustre
Kaolinite
Dull (or earthy) minerals exhibit little to no luster, due to coarse granulations
which scatter light in all directions, approximating a Lambertian reflector. An
example is kaolinite.[3] A distinction is sometimes drawn between dull minerals
and earthy minerals,[4] with the latter being coarser, and having even less
lustre.
Greasy lustre
Moss opal
Greasy minerals resemble fat or grease. A greasy lustre often occurs in
minerals containing a great abundance of microscopic inclusions, with
examples including opal and cordierite.[2] Many minerals with a greasy
lustre also feel greasy to the touch.[5]
Metallic lustre
Pyrite
Metallic (or splendant) minerals have the lustre of polished metal, and
with ideal surfaces will work as a reflective surface. Examples include
galena,[6]pyrite[7] and magnetite.[8]
Pearly lustre
Muscovite
Pearly minerals consist of thin transparent co-planar sheets. Light
reflecting from these layers give them a lustre reminiscent of pearls.[9]
Such minerals possess perfect cleavage, with examples including
muscovite and stilbite.[2]
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Resinous lustre
Amber
Resinous minerals have the appearance of resin, chewing gum or
(smooth surfaced) plastic. A principal example is amber, which is a
form of fossilized resin.[10]
Silky lustre
Satin spar variety of gypsum
Silky minerals have a parallel arrangement of extremely fine
fibres,[2] giving them a lustre reminiscent of silk. Examples include
asbestos, ulexite and the satin spar variety of gypsum. A fibrous
lustre is similar, but has a coarser texture.
Submetallic lustre
SphaleriteSubmetallic minerals have similar lustre to metal, but are
duller and less reflective. A submetallic lustre often occurs in nearopaque
minerals with very high refractive indices,[2] such as sphalerite,
cinnabar and cuprite.
Vitreous lustre
Quartz
Vitreous minerals have the lustre of glass. (The term is derived from
the Latin for glass, vitrum.) This type of lustre is one of the most
commonly seen,[9] and occurs in transparent or translucent minerals
with relatively low refractive indices.[2] Common examples include
calcite, quartz, topaz, beryl, tourmaline and fluorite, among others.
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Waxy lustre
Jade
Waxy minerals have a lustre resembling wax. Examples include jade[11]
and chalcedony.[12]
Optical phenomena
Asterism
Sapphire cabochon
Asterism is the display of a star-shaped luminous area. It is seen in
some sapphires and rubies, where it is caused by impurities of
rutile.[12][13] It can also occur in garnet, diopside and spinel.
Aventurescence
Aventurine Aventurescence (or aventurization) is a reflectance
effect like that of glitter. It arises from minute, preferentially
oriented mineral platelets within the material. These platelets are
so numerous that they also influence the material's body colour. In
aventurine quartz, chrome-bearing fuchsite makes for a green stone
and various iron oxides make for a red stone.[12]
Chatoyancy
Tiger's eye
Chatoyant minerals display luminous bands, which appear to move as the
specimen is rotated. Such minerals are composed of parallel fibers (or
contain fibrous voids or inclusions), which reflect light into a direction
perpendicular to their orientation, thus forming narrow bands of light.
The most famous examples are tiger's eye and cymophane, but the effect
may also occur in other minerals such as aquamarine, moonstone and
tourmaline.
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Colour change
Alexandrite
Color change is most commonly found in Alexandrite, a variety of
chrysoberyl gemstones. Other gems also occur in color-change
varieties, including (but not limited to) sapphire, garnet, spinel.
Alexandrite displays a color change dependent upon light, along with strong pleochroism. The gem
results from small scale replacement of aluminum by chromium oxide, which is responsible for
alexandrite's characteristic green to red color change. Alexandrite from the Ural Mountains in Russia
is green by daylight and red by incandescent light. Other varieties of alexandrite may be yellowish
or pink in daylight and a columbine or raspberry red by incandescent light. The optimum or "ideal"
color change would be fine emerald green to fine purplish red, but this is exceedingly rare.
SchillerLabradorite
Schiller, from German for "twinkle", is a term used to describe the
metallic iridescence originating from below the surface of a stone,
that occurs when light is reflected between layers of minerals. It is
seen in moonstone and labradorite and is very similar to
adularescence and aventurescence.[14]
appearance of material without regard to clolour-metallic silky
glossy
COLOUR :some colours
determined by molecular
structure ex.malachite, azurite,
chalcopyrite some because of
impurities found the crystal.
S T R E A K : c o l o u r o f t h e g r o u n d
p o w d e r o f a n y m i n e r a l E x .
M a l a c h i t – g r e e n , f l u o r i t e –
p u r p l e / w h i t e
TRANSPARENCY: Transparency Definition: Transparency refers to the degree to which light can
pass through a mineral.
Terminology: Opaque - no light can pass through the mineral;
Translucent - light can pass through the mineral but is diffused so that images cannot be seen
clearly;
Transparent– light can pass through the mineral and images can be seen clearly.
1. Transparency –light rays pass through 2.translucent-light pass through but diffused 3.opaquelight
doesnot pass through.
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Magnetite
(III) STRUCTURE :particular arrangement of the individual crystals – fine medium,or coarse,
coarse grained fibrous, separable divergent rdiating
HARDNESS: as corundum. The table below shows comparison with absolute hardness measured by a
sclerometer, with pictorial examples.[7][8]
Mohs hardness Mineral Chemical formula Absolute hardness Image
1
Talc Mg3Si4O10(OH)2 1
2 Gypsum
CaSO4·2H2O
3
3 Calcite CaCO3 9
4 Fluorite CaF2 21
5 Apatite Ca5(PO4)3(OH–,Cl–,F–) 48
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Mohs hardness Mineral Chemical formula Absolute hardness Image
6 Orthoclase Feldspar KAlSi3O8 72
7 Quartz SiO2 100
8 Topaz Al2SiO4(OH–,F–)2 200
9 Corundum Al2O3 400
10 Diamond C 1600
(IV) Relative resistence being scratched ten minerals are selected to measure the degree of
hardness from 1to 10
1. Talc 2.gypsum 3.calcite 4.fluorite 5.apatite 6.feldspar 7.quartz 8.topaz 9.corundum
10.diamond. ex.fingre nail has 2.5 hardness knife has 5.5 hardness
(V) SPECIFIC GRAVITY :The ratio between the weight of a given object and the weight of an
equal volume of water ; object weighed in air and then weighed in water and divide
weight in an airby the difference of th etwo weights.
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IMPORTANT MINERALS OF THE EARTH CRUST
FELDSPAR: Silicon & Oxygen Are Common Elements ,Sodium,
Potassium Calcium Aluminium Are Found In Specific Variety. ½ The
Earth Crust Consists Of Feldspar.Light Cream To Salmon Pink Colour
Used In Ceramics And Glass Making.
QUARTZ:important component of sand
granite.consists of silica, hard mineral,
insoluble in water it is white ore coloruless
used INRADO OR RADOR
YROXENE :consists of calcium aluminum magnesium iron silica, it forms 10%
of earth crust, found in meteorites,green or black in colour
OLIVINE:Magnesium,Iron, Silica are major elements,used in jewellary,
greenish crystal, found inbasaltic rocdk
AMPHIBOLE: aluminium, calcium silica, iron magnesium are
major elements. They form 7% of earth crust, green or black colour
, used in asbestos industry, hornblende is a;nother formof amphibole
MICA:consists of potassium, aluminium, magnesium iron silica . Form 4%
Of the earth crust. Found in basaltic rock
IGNEOUS ROCKS; 1. They are primary rocks 2.formed due to cooling of lava
3. They are two types intrusive & extrusive rocks
Extrusive rocks have small grains because of sudden cooling intrusive rocks have bigger grains due
to slow cooling4.they are hard 5. Do not contain fossils 6. Do not allow water to percolate
through them 7. No layers
SEDIMENTARY ROCKS:1. Formed Due To Sedimentation 2. Consists Of Layers 3. Contain Fossils
4.The Process Of Sedimentary Rock Formation Is Called Lithification 5. They Are Three Types . A.
Mechanically Formed B.Chemically Formed 3. Organically Formed.
METAMORPHIC ROCKS: 1.Formed Due To Recrystalization 2.Formed Due To Pressure And
Temperature 3. Very Smooth
4. Consists of layers sime times very preceious stones
Type of rock
Igneous rock Sedimentary rockMetamorphic rock
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Granite Sandstone Slate
CLASSIFICATIONOF MINERALS
METALLIC MINERALS NON METALLIC MINERALS
FERROUS NON FERROUS PRECIOUS ORGANIC INORGANIC
IRON COPPER GOLD COAL SULPHAR ROCKS
Rocks are aggregate of one or more minerals,they may be hard or soft in varied colours, they do not
have definite chemical composition.
Petrology is the science of rocks. Petrologist who studies the scientific methods of rocks.
ROCK CYCLE
A diagram of the rock cycle. Legend: 1 = magma; 2 =
crystallization (freezing of rock); 3 = igneous rocks; 4 =
erosion; 5 = sedimentation; 6 = sediments&sedimentary
rocks; 7 = tectonic burial and metamorphism; 8 =
metamorphic rocks; 9 = melting.
Rock cycle is a continuous process through which old rocks
are converted into new rocks. Igneous rocks are changed
into metamorphicor sedimentary rocks. Metamorphic rocks
afurther change into magma