Download ppt - Mahopac Voyagers!

Minerals
• Naturally occurring uniform (homogeneous)
substances that are inorganic. (Not formed
by or from living things.)
• Minerals have definite physical and chemical
properties.
• Only a few minerals are found everywhere
making up most of the rocks on Earth.
– Quartz, Feldspar, Calcite, Mica, Magnetite
• Oxygen and Silicon make up for most of the
mass of these minerals.
Rocks
• Most rocks are composed of one
or more minerals
–One mineral = monominerallic
–Two or more = polyminerallic
• Geologists classify rocks based
upon their origin
Rock Types
1.Sedimentary
2.Igneous
3.Metamorphic
Sedimentary Rocks
• Most are composed primarily of the
weathered remains of other rocks.
• Usually formed by compression and
cementation of sediments.
• Grains are usually rounded by
abrasion and deposited in layers.
• Relatively thin layer at the earth’s
surface.
Igneous Rocks
• Form by the crystallization of molten magma
or lava.
• From the crystal size we can infer the rate of
cooling
– Very Fast cooling can produce a glass (no visible
crystals)
– Slow cooling allows visible crystals to form
– Crystal size often varies with depth of formation
• Deep – slow cooling with large crystals
Metamorphic Rocks
• Form when sedimentary, igneous or
metamorphic rocks are changed by heat
and/or pressure.
• Recrystallization without melting.
• Change deep within the earth.
• Metamorphic rocks often show foliation
(mineral alignment – Ex. schist) or banding
(separation of minerals – Ex. Gneiss) and high
in density.