Transcript Minerals and Rocks - Pleasant Grove Middle School

Minerals and Rocks
Rocks
• Aggregates
(mixture—can be
separated) of
minerals.
Minerals
• Four Characteristics:
– Naturally occurring
– Inorganic (was never
alive)
– Solid
– Possesses a definite
chemical structure
Properties of Minerals
• Crystal form—
external expression of
internal structure
Properties of Minerals
• Color—unreliable in
identifying minerals
Properties of Minerals
• Streak—the color of a
mineral in its powder
form—obtained by
rubbing the mineral
across a hard,
unglazed porcelain
Properties of Minerals
• Hardness—resistance
of a mineral to
abrasion or scratching
– Mohs scale—hardness
scale ranging from 10
(hardest) to 1 (softest)
– Diamond is 10, talc is
1
Properties of Minerals
• Cleavage—tendency
of a mineral to break
along planes of weak
bonding
Properties of Minerals
• Fracture—do not exhibit cleavage when
broken
• Specific gravity—the weight of a mineral
compared to the same volume of water
Mineral Groups
• Silicates
– Silicon and oxygen are the two
most abundant elements in
the Earth’s crust; they form
silicates
– All have the same basic
structure—the silicon-oxygen
tetrahedron—four oxygen
atoms surrounding a silicon
atom
– Other elements join the
tetrahedrons together in
chains, sheets, or threedimensional networks.
– Feldspars are most abundant,
with quartz second
Mineral Groups
• Carbonates
– Calcite
• Limestone—used in
building and paving
• Marble—used
decoratively
• Halite (salt) and
Gypsum also found in
sedimentary rock
Mineral Resources
• Reserves—already identified deposits
from which minerals can be extracted
profitably
• Ores—useful metallic minerals that can be
mined at a profit
• Changing economic factors determine
whether a deposit is profitable to extract