Geosciences
Safwan
Lec6_RxsMinerals.pptxWhat is a mineral?
What is a rock?
Three types of rocks and how they form.
Minerals: the building blocks of rocks
A mineral:
is naturally occurring
is inorganic
has a definite chemical composition
has an ordered internal structure of atoms
Quartz
Minerals are made of elements
(Si, O, K, Al, Fe, Mg, Ca, C, Na, U, etc…)
THESE are the vessels for radioactive elements we use for age dating!
Ordered internal structure?
Silica tetrahedra: the building blocks of silicates.
Ex: Muscovite Mica
KAl2Si3O10(OH)2
Find a mineral on your table – how did you know it was a mineral?
The way the atoms arrange themselves controls the way the minerals grow. Silicates, the most common mineral type, all contain the basic silica tetrahedron. Sheet silicates grow in sheets, salt is cubic and grows in cubes.
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Muscovite: K Al2 Si3 O10 (OH)2
Biotite: K (Mg, Fe)3 Al Si3 O10 (OH)2
Mg and Fe = MAFIC minerals
Mafic dark colored, higher density
Rocks = amalgamations of minerals. Rocks can also be mafic or felsic depending on what type of minerals they contain
Light colored rocks = felsic Dark colored rocks = mafic
We also look at the size/shape of the minerals in the rock to help classify it
Igneous, Sedimentary, Metamorphic
Both are the mineral Mica
Both are silicates (Si)
No Mg,Fe = Felsic minerals
Felsic light colored, lower density
Muscovite: K Al2 Si3 O10 (OH)2
Biotite: K (Mg, Fe)3 Al Si3 O10 (OH)2
Mg and Fe = MAFIC minerals
Mafic dark colored, higher density
Rocks = amalgamations of minerals. Rocks can also be mafic or felsic depending on what type of minerals they contain
Light colored rocks = felsic Dark colored rocks = mafic
We also look at the size/shape of the minerals in the rock to help classify it
Igneous, Sedimentary, Metamorphic
Both are the mineral Mica
Both are silicates (Si)
No Mg,Fe = Felsic minerals
Felsic light colored, lower density
Handout part I: Minerals and Rocks (workbook)
Igneous rocks – rocks that cool and solidify from magma or lava.
Magma – below Earth’s surface; Lava – on Earth’s surface
Processes: melting, cooling, crystallization/solidification
Common igneous rocks:
Granite Continents
Basalt Ocean floor
Question – What does the color tell us?
Igneous rocks:
Cools and solidifies (i.e., forms) on the surface of Earth
Formed from lava (molten rock that erupts on surface)
Called volcanic or extrusive rocks – Texture = small crystals (cooled quickly)
Cools and solidifies (i.e., forms) inside Earth (molten rock that never erupts)
called plutonic or intrusive rocks - Texture = large crystals (cooled slowly, crystals had time to grow)
Form as lava or magma cools and crystallizes
Terminology alert!!
Look at these two rocks…similarities? Differences? Can you find a rock on your table that you would call igneous?
Which of the following rocks clearly looks like it is made up of pieces/chunks of other rocks?
B.
C.
A.
Sedimentary rocks
Form when sediment (pieces of a pre-existing rock, pieces of shell) is compacted and cemented together. Form in layers.
About 75 percent of all rocks on the surface of continents are sedimentary.
Processes = weathering (break down of rocks), erosion, deposition, compaction, cementation (lithification)
Can you find one on your table?
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Metamorphic rocks
“Changed form” rocks. Produced from preexisting rocks.
Processes = heat and/or pressure unlike those in which the rock originally formed.
NO MELTING!
If these rocks melted and then cooled into rock again, they would be ______ rocks.
Granite = igneous
Gneiss = metamorphic
Handout – Rock types (workbook)
Find one on your table!
Metamorphism happens when rocks are subjected to heat, pressure, or chemical alteration. If rocks melted and then cooled into rock again, they would be igneous rocks.
Don’t forget to turn in your handouts for participation credit.
Name clear on front page!
