Transcript EarthScience_Topic 8-Minerals and Rocksx

Minerals and Rocks
5 Characteristics of Minerals
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Naturally Occurring
Inorganic
Found as a solid in nature
Formed from elements or compounds
Definite chemical make up and regular atomic
structure
By that definition…
• Is a snow flake a mineral?
A.
• Minerals are classified according to their
physical and chemical properties.
Physical Properties
• 1) Color: easiest to recognize but not very
reliable
– Example: quartz- comes in several different colors
– Example: calcite and halite- both can be
transparent and/or same color
Physical Properties
• 2) Streak- the color of a mineral when
powdered
– Test: rub the mineral across a piece of unglazed
ceramic tile
Physical Properties
• 3) Luster: the way a mineral reflects light
– Metallic- looks like shiny metal
– Non-Metallic- does not look like shiny metal (can
be dull, waxy, glassy, etc)
Physical Properties
• 4) Hardness: a minerals ability to scratch or be
scratched
– Test: Use an edge of your mineral and try to
scratch a glass plate
– Moh’s hardness scale: 10 common minerals
placed in order of hardness
• The higher the number the harder the mineral
Physical Properties
• 5) Cleavage: the tendency of a mineral to split
along smooth, flat surfaces called plains
– Test: Look at the mineral carefully and check for
light reflecting off of flat surfaces
Physical Properties
• 6) Fracture: When a mineral breaks into pieces
with uneven surfaces
Physical Properties
• 7) Specific gravity: the ratio between the
weight of a substance and the weight of the
substance in an equal volume of water
Physical Properties
• 8) Special Properties: unique properties some
minerals have
– Examples: Halite- tastes salty
• Magnetite- magnets are attracted to it
• Calcite- bubbles with HCL (acid test)
B.
• Minerals are grouped according to their
chemical properties
• 1. The elements silicon and oxygen combine
to form tetrahedral units
• 2. The physical properties of minerals depend
upon the internal arrangement of atoms.
• Diamond- Jewelry, Cutting hard surfaces
• Graphite- pencil lead, lubricant
• Both 100% carbon
• 3. Of the thousands of known minerals, only a
few are found almost everywhere
• 4. If you know how to identify about 12 of the
most common minerals you will be able to
identify minerals in most rocks you are likely
to find.
• 5. Nearly all rocks are composed of one or
more minerals
• 6. Minerals are the building blocks of most
rocks.
– Some exceptions include coal.
• Stuff away
• Characteristics of a mineral
• Physical Properties of a mineral
• ?’s in np
Igneous rocks
• Solidification of molten material (magma)
• Named based upon their environment of
formation.
Intrusive Igneous Rocks
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AKA. Plutonic
Rate of cooling: slow to very slow
Size of crystals: 1mm to more than 10mm
Texture: Coarse/very coarse
Extrusive Igneous Rocks
• AKA. Volcanic
• Rate of cooling: fast to very fast
• Size of crystals: less than 1mm to noncrystalline
• Texture: glassy/fine
Vesicular
• Gas bubbles
Felsic
Mafic
Non-crystalline
• No visible crystals
Sedimentary Rocks
• Deposition, burial, compaction and
cementation of sediments
Clastic Sedimentary Rocks
• Classified by grain size.
• Formed by: deposition, burial, compaction
and cementation of sediments
• Ex: Siltstone, sandstone, conglomerate,
breccia, shale
Crystalline Sedimentary Rocks
• Classified by composition
• Formed by: compaction and cementation.
Crystals from chemical precipitates and
evaporates
• Ex. Rock salt, gypsum, dolostone
Bioclastic sedimentary rocks
• Classified by composition
• Formed from: cemented shell fragments and
biologic origin
• Ex. Limestone
• Formed from plant remains
• Ex: coal
• 1) Formed in horizontal layers on Earth’s
surface because that’s where all of the
weathering , erosion and biologic activity
takes place
• 2) Fossils are almost exclusively found in
sedimentary rocks because formation of the
other rock types alters or destroys them.
• Igneous melts them
• Metamorphic deforms them
• 3) Fossils provide…
Metamorphic Rocks
• Formed directly from any type of rock
• Extreme heat and pressure cause
metamorphism
Changes in Rocks due to
Metamorphism
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Recrystallization of unmelted material
Density increases
Foliation- minerals are aligned
Banding- thin layers of alternating minerals
Regional Metamorphism
• Occurs when large areas of rock are under
intense heat and pressure
• Associated with mountain building
Contact Metamorphism
• Occurs when molten rock comes in contact
with surrounding rock
• Heat alters the rock it comes in contact with
• Helps to establish relative ages of rocks
Classification of Metamorphic Rocks
• Texture- including foliated or banding
composition
Degree of metamorphism
• Can be a small alteration to major changes
depending on the amount of heat and
pressure
Parent Material
• What the rock used to be before it changed
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Shale Slate (low)
Shale Phyllite (medium)
Shale Schist (medium)
Shale gneiss (high)
• The deeper under ground, the more heat and
pressure and the greater the change
The rock cycle
• Continuing change from one rock type to
another rock type