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Minerals
A mineral is a naturally occurring, inorganic solid
with a specific chemical composition and a
definite crystalline structure.
Naturally occurring means formed by natural
processes, so that DOES NOT include
synthetically created diamonds and other gems.
Inorganic means that they aren’t alive, and never
were. Therefore coal and sugar would NOT be
minerals.
Solids with a specific composition mean that they
are solids, not liquids or gases. It also means that
they are made up of specific elements or
compounds. Quartz is made up of silicon and
oxygen. Other minerals may also be made up of
silicon and oxygen, but quartz has a specific
arrangement and proportion of these elements that
is unique to quartz.
A crystal is a solid in which the atoms are arranged
in repeating patterns.
Minerals from Magma-the type and amount of
elements in magma help determine which minerals
will form. If the magma cools slowly, beneath the
earth’s surface, the large crystals will grow. If the
magma reaches the surface and therefore cools
quickly, the minerals sizes will be small. One
example of a rock that forms from magma is
granite.
Minerals from Solution-when crystals precipitate
(sink) out of a solution, or when the liquid
evaporates, leaving the crystals behind. One
example is gypsum.
Mineral groups-there are 3000 minerals found in
the Earth’s crust, but only about 30 of these are
common.
Identifying mineralsColor-sometimes caused by the presence of trace
elements or compounds in a mineral.
Luster-the way that a mineral reflects light
(metallic or nonmetallic)
Texture-how it feels to the touch, such as smooth,
rough, ragged, greasy, soapy or glassy.
Streak-the color of a mineral when it is broken up
and powdered. Usually we drag the rock across a
porcelain plate to see its streak color.
Hardness-how easily a mineral can be scratched.
Moh’s Hardness Scale is a scale in which an
unknown mineral’s hardness is compared to the
known hardness or ten minerals.
Cleavage and fracture-how a mineral breaks. If
it breaks cleanly, along certain planes, then it is
said to have cleavage. If it breaks jaggedly, then it
is said to have fracture.
Density- is mass divided by volume.
Mineral UsesOres-a mineral that contains a useful substance
that can be mined for a profit, such as iron.
Gems-valuable minerals prized for their beauty
and rarity. Examples-diamond, ruby, sapphire, etc.