Download Rocks & Minerals

Rocks & Minerals
Minerals
• There are about 3000 known minerals
• Minerals are made of elements (either a single
element or a combination of elements)
• Examples of Minerals
– Gold: a mineral made of one element (gold…Au)
– Calcite: a mineral made of 3 elements (calcium, carbon,
and oxygen…CaCO3)
gold
calcite
Scientific Requirements for a
Substance to be a Mineral
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Must be naturally occurring (they must occur in nature)
Must be inorganic (not made of living things)
Must be crystalline (have a crystal structure)
Must be solid (minerals are not gases and liquids)
Must have definite physical and chemical properties
How do we identify minerals?
• By color: a red mineral is most likely not gold
(which is a shiny gold color) or biotite (which is a
black color)
• By luster: the luster of a mineral describes how
shiny it looks (silver has a metallic luster and pure
quartz has a glassy luster)
• By streak color: What color is the streak when a
mineral is rubbed on a porcelain plate?
• By hardness: How hard is the mineral? (The Mohs
hardness scale uses numbers to describe hardness)
Mohs Mineral Hardness Scale
1) Talc
Softest
2) Gypsum
3) Calcite
1
5
4) Flourite
9
5) Apatite
2
6) Feldspar
6
7) Quartz
3
8) Topaz
7
9) Corundum
10) Diamond
Hardest
4
8
10
Rocks
• Rocks are mixtures of minerals
• Most rocks are composed of at least 2 minerals
• Example of a rock:
– Granite: contains 75% feldspar, 20% quartz, and 5% mica
Classifying Rocks
• Rocks are classified by how they formed and what
they’re made of
• There are 3 general classes of rocks
– Igneous Rocks…are formed when lava and magma
crystallize to form solid rock
– Metamorphic Rocks…are formed when an existing rock
is partially melted, squeezed, or both
– Sedimentary Rocks…are formed when sediments (sand
clay, and silt) are compressed and become solid rock
Examples of Different Classes of Rocks
Igneous
Granite cooled very slowly
Obsidian cooled very quickly
Examples of Different Classes of Rocks
Metamorphic
Gneiss has bands because it was folded and compressed
Examples of Different Classes of Rocks
Sedimentary
Sandstone is made of sand grains
Shale is made of clay particles