Common Rock-Forming Minerals with K. Guru Brahmam
K. Guru Brahmam
K. Guru Brahmam
Lecturer
Department of Geology
K. Guru Brahmam
Six Common Rock-Forming Minerals
The six minerals amphibole, feldspar, mica, olivine, pyroxene,
and quarts are the most common rock-forming minerals and are
used as important tools in classifying rocks, particularly igneous
rocks.
Except for quartz, all the
minerals listed are actually mineral
groups.
However, instead of trying to separate all the minerals which
make up a group, which is often not possible in the field, they
are dealt with here as a single mineral with common
characteristics.
K. Guru Brahmam
Quartz and feldspar are light- coloured minerals; mica, pyroxene.
amphibole and olivine are dark- coloured. The colour ofa rock will
betermined by the proportions of light and dark-coloured minerals
present.
If most of the grains are quarts and feldspar then the overall appearance
of the rock will be light, while the opposite will be true if the minerals
are mainly mica, pyroxene, amphibole or olivine.
The colour of a rock with between 25 and 50% dark minerals is
Intermediate.
K. Guru Brahmam
Common Rock-forming Minerals
Quartz
Quartz which is usually called silica, is one of the most common
minerals in the Earth’s crust.
Quartz is made up of silicon dioxide (SiO
z
)
Quartz crystals are usually hexagonal and prismatic in shape.
Pure quartz is colourless, although the presence of impurities may
give a range of colours, such as violet, pink and orange.
Quartz is the raw material for making glass.
K. Guru Brahmam
Plagioclase
Feldspar
Plagioclase
feldspar
i
s sodium
-
or
calcium – rich
feldspar.
The chemical
composition ranges from sodium
aluminum
silicate
,
NaAlSi
3
O
8
to
calcium
aluminum
silicate, CaAl
2
S
2
O
8
Plagioclase
feldspar
crystals
usually
occur
as
study
prisms.
Plagioclase
feldspar
is
generally
white
to
grey
and
ha
s vitreous luster.
Plagioclase
feldspar
is
an
important
industrial
minera
l
use
d
in ceramics.
K. Guru Brahmam
Alkali
Feldspar
Alkali
feldspar
is
another
member
of
the
family of feldspar minerals.
Alkali
feldspar (Potassium
aluminum
silicate
(K,Na)AlSi
3
O
8
)
are
rich
In alkali
metal ions.
Alkali
feldspar
crystals
usually occur
as study prisms.
Alkali
feldspar
is
commonly pink
to
white.
Alkali
feldspar
is used
a
s
raw
material to
make
porcelain.
K. Guru Brahmam
Micas
•
Micas
are
a
family silicate minerals.
•
Micas
are made
up
of varying
amounts
of
potassium,
magnesium, iron, as well as aluminum,
Silicon
and
water.
•
Micas
form
flat, book-like
crystals
that
split
into
Individual
sheets,
separating
into
smooth
flakes
along
the
cleavage
planes.
•
They are common minerals in intrusive
igneous
rocks, and can also be found in sedimentary and
metamorphic rocks.
•
Biotite is
dark
, black or brown
mica;
muscovite
is
light-colored or
c
lear mica.
K. Guru Brahmam
Amphiboles
o
Amphiboles
a
re
a family silicate minerals
o
Amphibole minerals generally contain
iron,
magnesium,
calcium
a
nd
aluminum
as
well as
silicon, oxygen, and water.
o
Amphiboles
form
prismatic
or
needle-like
crystals.
o
Amphibole
is
a component of many igneous and
metamorphic rocks.
o
Hornblende
is
a
common member
of the
amphibole
group
of
rock-
forming
minerals.
K. Guru Brahmam
Pyroxene
Pyroxenes are
a
family
of silicate
minerals.
Pyroxene
minerals
generally
contain magnesium
,
iron,
calcium
a
nd aluminium
as
well
as
silicon
and oxygen.
Pyroxenes form
short
or
columnar
prismatic
crystals.
P
yroxene
is
a component
in
many
igneous
and
metamorphic
rocks.
Pyroxene
crystals
are commonly
faceted
as
gemstones
for instance,
precious
Jade
(Jadeite)
is
a pyroxene.
K. Guru Brahmam
Olivine
•
Olivine
i
s
a
silicate
mineral.
•
Olivine
((Mg,
Fe)
2
Si0
4
) contains
ir
on
and
magnesium.
•
O
livine
is
a
green,
glassy
mineral.
•
Olivine
is
common
in
mafic
a
nd ultramafic rocks.
•
Clear
and
transparent
olivine
crystals
are
commonly
faceted
as
gemstones
K. Guru Brahmam
Calcite
•
Calcite is
a
carbonate
mineral.
•
Calcite
is
made up of Calcium Carbonate(Caco
3
).
•
Calcite is generally white to clear, and is easily scratched with
knife.
•
Calcite is a common sedimentary mineral that is the major component
of calcareous sedimentary rocks such as limestone. Metamorphism of
limestone produces marble
.
K. Guru Brahmam
K. Guru Brahmam
Thank you
Explore the six common rock-forming minerals including quartz, feldspar, mica, olivine, pyroxene, and amphibole with insights from K. Guru Brahmam, a lecturer in the Department of Geology. Learn how these minerals are essential tools in classifying rocks and determining their color and composition. Delve into the properties of quartz, plagioclase feldspar, and alkali feldspar, and understand their industrial significance in various applications. Enhance your knowledge of rock-forming minerals through detailed descriptions and visual aids.
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Presentation Transcript
Rock Forming Minerals K. Guru Brahmam
K. Guru Brahmam Lecturer Department of Geology K. Guru Brahmam
Six Common Rock-Forming Minerals The six minerals amphibole, feldspar, mica, olivine, pyroxene, and quarts are the most common rock-forming minerals and are used as important tools in classifying rocks, particularly igneous rocks. Except for quartz, all theminerals listed are actually mineral groups. However, instead of trying to separate all the minerals which make up a group, which is often not possible in the field, they are dealt with here as a single mineral with common characteristics. K. Guru Brahmam
Quartz and feldspar are light- coloured minerals; mica, pyroxene. amphibole and olivine are dark- coloured. The colour ofa rock will betermined by the proportions of light and dark-coloured minerals present. If most of the grains are quarts and feldspar then the overall appearance of the rock will be light, while the opposite will be true if the minerals are mainly mica, pyroxene, amphibole or olivine. The colour of a rock with between 25 and 50% dark minerals is Intermediate. K. Guru Brahmam
Common Rock-forming Minerals Quartz Quartz which is usually called silica, is one of the most common minerals in the Earth s crust. Quartz is made up of silicon dioxide (SiOz) Quartz crystals are usually hexagonal and prismatic in shape. Pure quartz is colourless, although the presence of impurities may give a range of colours, such as violet, pink and orange. Quartz is the raw material for making glass. K. Guru Brahmam
Plagioclase Feldspar Plagioclase feldspar is sodium- or calcium rich feldspar. The chemical composition ranges aluminum silicate, NaAlSi3O8 calcium aluminum silicate, CaAl2S2O8 from sodium to Plagioclase feldspar crystals usually occur as study prisms. Plagioclase feldspar is generally white to grey and has vitreous luster. Plagioclase feldspar is an important industrial mineral used in ceramics. K. Guru Brahmam
Alkali Feldspar Alkali feldspar is another member of the family of feldspar minerals. Alkali feldspar (Potassium aluminum silicate (K,Na)AlSi3O8) are rich In alkali metal ions. Alkali feldspar crystals usually occur as study prisms. Alkali feldspar is commonly pink to white. Alkali feldspar is used as raw material to make porcelain. K. Guru Brahmam
Micas Micas are a family silicate minerals. Micas are made up of varying amounts of potassium, magnesium, iron, as well as aluminum, Silicon and water. Micas form flat, book-like crystals that split into Individual sheets, separating into smooth flakes along the cleavage planes. They are common minerals in intrusive igneous rocks, and can also be found in sedimentary and metamorphic rocks. Biotite is dark, black or brown mica; muscovite is light-colored or clear mica. K. Guru Brahmam
Amphiboles o Amphiboles are a family silicate minerals o Amphibole minerals generally contain iron, magnesium, calcium and aluminum as well as silicon, oxygen, and water. o Amphiboles form prismatic or needle-like crystals. o Amphibole is a component of many igneous and metamorphic rocks. o Hornblende is a common member of the amphibole group of rock- forming minerals. K. Guru Brahmam
Pyroxene Pyroxenes are a family of silicate minerals. Pyroxene minerals generally contain magnesium, iron, calcium and aluminium as well as silicon and oxygen. Pyroxenes form short or columnar prismatic crystals. Pyroxene is a component in many igneous and metamorphic rocks. Pyroxene crystals are commonly faceted as gemstones for instance, precious Jade (Jadeite) is a pyroxene. K. Guru Brahmam
Olivine Olivine is a silicate mineral. Olivine ((Mg, Fe)2Si04) contains iron and magnesium. Olivine is a green, glassy mineral. Olivine is common in mafic and ultramafic rocks. Clear and transparent olivine crystals are commonly faceted as gemstones K. Guru Brahmam
Calcite Calcite is a carbonate mineral. Calcite is made up of Calcium Carbonate(Caco3). Calcite is generally white to clear, and is easily scratched with knife. Calcite is a common sedimentary mineral that is the major component of calcareous sedimentary rocks such as limestone. Metamorphism of limestone produces marble. K. Guru Brahmam
Thank you Thank you K. Guru Brahmam
