Rocks and minerals

Rocks and Minerals
Science 2201


Grains of sand…


Many ongoing processes constantly
change the surface of the globe.


Our Earth is cyclic and restless.
In other words,
---everything on the earth
operates in cycles
---the surface of the earth
is constantly changing


Geology
• The science that
considers the
history of the
earth, as
recorded in rocks


Basic Structure of the Earth
• 8,000 miles in diameter

• lithosphere, hydrosphere, atmosphere

• 4 spherical regions:
– crust, mantle, outer core, inner core


Earth Structure



Rocks
• Igneous = formed by the cooling and
crystallization of magma (melted rock)
• Sedimentary = formed from accumulation
of weathered material (sediments)
• Metamorphic = formed from preexisting
rocks that have been transformed (changed)


Igneous, Sedimentary, Metamorphic
 Each type of rock records a different
complex past.
 Each type of rock can be changed from
one form to another and back again.
 geologists call these transformations the
“rock cycle”


Rock Cycle


What are Rocks? What are Minerals?

• Rocks

• Minerals

• An aggregate or
mixture of minerals.
• Composition can vary
• Most rocks are
composed of more
than one mineral

• Inorganic chemical
elements or
compounds found in
the Earth’s crust.
• > 3000 minerals are
found in Earth’s crust


Limestone made of Calcite


Granite contains 3 minerals.


Minerals
• minerals are the building blocks of rocks
• differ in composition and properties
See Minerals link on Pacing Guide
• Weinman Mineral Museum…you gotta go!

Crystal Form
• Pyrite, Fe2S

• Quartz, SiO2


Moh’s Hardness Scale
•
•
•
•
•

1.Talc
2.Gypsum
3.Clacite
4.Fluorite
5.Apatite

• 6.Orthoclase
• 7.Quartz
• 8.Topaz
• 9.Corundum
• 10.Diamond


Cleavage & Fracture

Physical Properties of Minerals
• Crystal form
• Hardness
• Plane of Cleavage

• Luster
• Color and Streak
• Specific Gravity


Mineral Luster
• the appearance of its surface as it reflects
light
• minerals of the same color can have
different luster.


Color and Streak
• Color: red rubies, or blue sapphires, same
mineral—corundum (Al2O3)
• Streak refers to the color of a mineral in its
powdered form, example – hematite


Specific Gravity
• A density measure
• compares weight of a volume of substance
to the weight of the same volume of water
• Example:

– cm3 pyrite weighs 5X as much as cm3 water
– cm3 gold weighs 20X more than cm3 water


Igneous Rock
• formed by cooling & crystallization
of magma.
• means “formed by fire”
• make up about 95% of the earth’s crust
• basalt (ocean floor) and granite (continents)
are common examples


Igneous Rock
• Extrusive
• Form at earth surface
Example-basalt
Fine texture
Small minerals
Fast cooling

• Intrusive
• Form inside crust
Example-granite
Course texture
Large minerals
Slow cooling


Igneous Rocks

Texture

Silica
Content
High

Medium

Low

Course

Granite

Diorite

Gabbro

Fine

Rhyolite

Andesite

Basalt

Glassy

Obsidian

Basalt (gl)

Vesicular

Pumice

Scoria