Minerals & Rocks
Honors Notes
A Mineral is a naturally occurring
Inorganic Solid with a definite
chemical composition and a
crystalline structure.
Lets put that in a list format:
1. Minerals are a naturally occurring substance.
2. Minerals are solids.
Two Major Types of Minerals
Silicate Minerals
◦ Contain silicon (Si) plus oxygen (O) or silicon
dioxide (SiO2).
◦ The most common rock-forming minerals
◦ May contain one or more other elements with the
silicon and oxygen.
3. Minerals have a definite chemical
composition.
EX: Feldspars are formed depending on what else
combines with the silicon and oxygen.
◦ Orthoclase- Si, O, K, AL
◦ Plagioclase- Si, O, Ca, Na
EX: Quartz composed of only Si and O
4. The atoms that make up minerals are
arranged in an orderly pattern (They form
crystals).
◦ Make up 96% of the Earth’s crust.
5. Minerals are inorganic. (They
were never alive.)
Earth’s oceanic crust is denser and contains a larger
percentage of silicates than continental crust.
Silicate Minerals
Two Major Types of Minerals
(cont’d)
Non-silicates
◦ Contain no silicon
◦ Many important mineral groups are not silicates.
◦ Non-Silicate Minerals include: carbonates,
(limestone, marble) oxides (hematite), halides
(halite/rock salt), sulfides (pyrite), sulfates
(gypsum), and native metals (gold, silver, copper).
◦ The non-silicate groups are a source of many
valuable ore minerals and building materials.
◦ To be an ore, a mineral must occur in large enough
quantities to be economically recoverable.
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Non--Silicate Minerals
Non
Non--Silicate Minerals
Non
Mineral appearance
Mineral appearance
Hardness
Luster
Specific gravity
Streak
Cleavage and fracture
How it looks like
What color is it?
Which one of the following is gold?
Identify by appearance.
Physical Properties
Hardness
A measure of how easily a mineral can be
scratched
Mohs Hardness Scale
◦ developed in 1812 by Friedrick Mohs (an Austrian mineral
expert) as a method to identify minerals.
Luster
The way a mineral reflects a light.
Either
metallic or nonmetallic
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Specific Gravity
The specific gravity of a mineral is the
ratio of its weight compared with
the weight of an equal volume of water.
Gold has specific gravity of
It means gold is
than water.
19
19 times heavier
19 times heavier
Cleavage is the way that mineral breaks.
Streak
Specific gravity
When a mineral is rubbed across a piece
of porcelain tile a streak of powdered
mineral is left behind.
Minerals that break along smooth, flat
surfaces have cleavage.
Mica has cleavage
Cleavage
and Fracture!...
Mineral that breaks uneven, rough, or
jagged surfaces have fracture.
Quartz has fracture
quartz
Atom Arrangement
Some physical properties are controlled
by the orderly arrangement of atoms in a
mineral’s structure.
The arrangement of atoms and the bonds
between them can reflect the way a
mineral breaks, how hard it is, and what
types of crystal shape it has.
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Crystal Shape – Types of
Symmetry
Plane
Name
1
=Basal
2
=Prismatic
3
=Cubic
3
=Rhombohedral
Which of these would halite be the shape of?
An illustration
appearance:luster,color and streak
An illustration
cleavage and fracture
Special Properties of Minerals
CLEAVAGE
FRACTURE
Identify the minerals below
for cleavage and fracture
Magnetic – use a magnet and see if it sticks
Taste – certain minerals have a specific taste
Fluorescence – glowing while under a U.V.
light
Phosphorescent – continues to glow after the
U.V. light is off
Radioactive – test minerals with a Geiger
counter
Double Refraction – Splits light rays into 2
parts. (see a double image) Look through
the mineral for the image.
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Rocks
Classify Rocks by how they form
A rock is a naturally formed consolidated
solid mixture made up of minerals, rock
fragments, or volcanic glass
◦ - Made up of magma or lava
when it cools and hardens
Igneous
Sedimentary
◦ - Made from sediments
Essential Minerals: always occur in the
rock
Accessory Minerals: sometimes occur in
rock
Metamorphic
◦ - Rocks changed by pressure &
heat
Igneous Rocks
Formed from lava or magma
◦ Lava : extrusive or volcanic
◦ Magma: Intrusive or plutonic (pillow-like)
Intrusive Igneous rocks
Formed from magma which cools and solidifies
below Earth’s surface
Cooling and solidification take a long time
resulting in large visible crystals (coarse-grained)
Extrusive Igneous Rocks
Small to no mineral crystals due to faster cooling
lava above Earth’s surface (fine-grained)
Occurs at volcanoes or through ocean floor
Sedimentary Rocks Formation
Sedimentary Rocks
Rock is a fused mixture of minerals. Some of
these minerals could be in bits and pieces of
other rocks.
Broken into pieces (clasts) through weathering
◦ Rock exposed at the surface is attacked by the weather
Water: enters cracks, expands, & breaks rocks
down
Rain: acidic dissolves minerals
Movement in rivers: collects at the bottom
Build very slowly in layers, until the environment
changes
◦ Compaction: pieces compact due to weight squeezing
them together
◦ Cementation: minerals acting as cement holding
sediments together
◦ Precipitation: water evaporates & minerals are left
behind
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Classifying Sedimentary Rocks
Clastic Rocks: pieces of other rocks
NonClastic Rocks
Minerals in water which evaporates to
leave behind deposits (rocks) or fossil
materials that compact into rock.
Ex:
◦
◦
◦
◦
◦
Metamorphic Rocks
Form from pre-existing igneous,
sedimentary, or metamorphic rocks, as a
result of temperature and pressure
changes
3 types of changes:
Rearrangement of mineral grains
2. Enlargement of crystals
3. Change in chemistry of rock
Foliation: Foliated textures in
metamorphic rocks have lots of layers or
bands.
Non-Foliated: metamorphic textures
include rocks whose grains are in more
random orientations. (no bands)
◦ Tend to have random crystal orientation and
uniform grain size.
◦ Mineral grains tend to grow larger as
metamorphism increases.
Characteristics of
Metamorphic Rocks
Foliation
Nonfoliated
Limestone: calcite and seashells
Rock salt: halite
Rock gypsum: gypsum
Chert: Quartz
Coal: fossil materials
Characteristics of
Metamorphic Rocks
1.
1.
2.
3.
4.
5.
Hints for Identifying Rocks
Igneous
◦ crystals intersecting at angles
◦ size of the grain
Sedimentary
◦ layers of rock pieces
Metamorphic
◦ pressure created results in lines
◦ pressure and heat create grains in foliation (wavy
patterns)
◦ hardest of the 3 rocks
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Rock Cycle
Changes of rocks from one rock type to another
Magma
Metamorphic Rock
Igneous Rock
Sediments
cementation or compaction
Sedimentary Rock
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