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
Sedimentary Rock
 formed from the weathered material
carried by water, wind, or ice
 most common rocks in the upper crust
 cover over 2/3 of the earth’s surface
 sandstone, shale, and limestone
Sedimentary Rock
• Clastic
• Broken pieces of rock
• Particle deposition at
river bottom, beach,
or desert
• Cementation
• Ex-quartz mineral
forms sandstone
• Chemical
• Dissolved materials
precipitate from
solution
• Inorganic or organic
• Ex-calcite mineral or
calcium carbonate
from shells forms
limestone
Sedimentary Rocks
Sediment
Sedimentary Rock
Gravel and cobbles
Conglomerate
Sand
Sandstone
Silt and clay
Shale
Calcium carbonate
Limestone
Calcium sulfate
Gypsum
Sodium chloride
Halite
Metamorphic Rock
• ---formed from preexisting rocks (igneous,
sedimentary, or other metamorphic)
• ----metamorphic means “changing in form”
• ----marble and slate are common examples
Metamorphic Rock
• Foliated
• Elongated minerals
align in parallel layers
• H & P separates
minerals into parallel
layers
• Igneous granite to
metamorphic gneiss
• Nonfoliated
• Smooth, solid
homogenous blend of
minerals in rock
• H & P recrystallizes
rock
• Igneous limestone to
metamorphic marble.
Metamorphic Rock
Original Rock
Metamorphic Rock
Sandstone
Quartzite
Limestone
Marble
Shale
Slate, Schist
Granite
Gneiss
Metamorphic Rock
Origin
• Slate
• Quartzite
• Marble
from shale
from sandstone
from limestone
Discussion Question for Review
• Chapter 17 Try p. 362-363 Discussion
Questions 1-5, 7,9,10.
• Chapter 18 Try p. 387 Discussion
Questions 1,2,3,5.