5. Earth Materials and Minerals Flashcards
What are minerals? (3)
a) naturally occurring solids with b) fixed chemical composition
c) periodic array of atoms forming crystal structure
How many minerals are there? How many did we start off with? How did more become?
4000 known species
pre-solar nebula only had 12
more formed because of incongruent melting
What are sediments?
pieces of weathered rocks and minerals (boulders, cobbles, pebbles, sand, silt, mud, clay, nanoparticles)
What are melts?
molten rocks
no ordered arrangement of atoms
What are glasses?
frozen melts
no ordered arrangement of atoms
What are quartz?
- naturally occurring mineral
- the name tells the phase: SIO2 and trigonal symmetry
- fixed chemical composition
periodic arrangement of atoms
What is a phase?
a combination of composition and structure
- ex- quartz is SiO2 and trigonal symmetry
How many phases does SiO2 have?
7 phases (a-quartz, b quartz, tridymite, cristobalite, coesite, stihovite, liquid, )
What is an igneous rock and how do we classify them?
a rock that has crystallized from a melt
- classify based on silica content and extrusive/ intrusive
What is an intrusive/ extrusive igneous rock?
- intrusive/ plutonic- rocks that cooled slowly in earth’s crust. Have large crystals and coarse grained. Ex- granite
- extrusive- rocks that cooled quickly near or on surface of earth in volcanic eruptions. Fine grained. Ex- rhyolite
Do extrusive and intrusive igneous rocks have the same composition?
Yes
What is metamorphism?
- when rocks undergo solid-state changes that are enhanced by hot, mineral rich fluids
- any rock can be metamorphosed, making them different from origin rock
- ex- silica-rich igneous rocks (granite) or sediments metamorphones into gneiss . We see banding dark and light colors
What’s an example of metamorphism?
- silica-rich igneous rocks (granite) or sediments metamorphones into gneiss We see banding dark and light colors
What is granite?
- intrusive igneous rock
- high in silica content (felsic)
- in crust
- most commonly made up of alkali feldspar. Also contains plagioclase feldspar, quartz, and mica
What is rhyolite?
- extrusive igneous rock
- high in silica content (felsic)
- made of quartz, alkali feldspar, plgioclase feldspar
Are melts and glass minerals?
No
What’s the oldest stone tool?
2.5 Ma old
Give an example of how mineral diversity changed by life.
- trilobites grew calcite shells. Became survival tools
- humans grow apatite mineral in bones and enamel
- early bacteria got energy from minerals
What are the stages of earth and what are the dates?
Black Earth- 4.5 Grey Earth- 4.3 Blue Earth- 3.8 Red Earth- 3.5 White Earth- 540 Ma Green Earth- 520 Ma- now
What was the black earth?
- 4.5 Ma
- dust and rocks just accreted
- magma ocean cooling, leaving black basaltic surface
What was the grey earth?
- 4.3 Ma
- incongruent melting gave way to granite
- zircons still found today in Australia (4.4) and Canada (4.2)
What was the blue earth?
- 3.8
- first known water was stable turned planet blue with oceans
- we know the age because pillow basalts off Greenland were 3.8 Ga and formed underwater
What was red earth?
- 3.5 Ga
- cynobacteria (First photosynthesizing forms of life) pumped oxygen into air, seas
- oxidizing all minerals in seas, rained down, forming banded iron formations
What was the white earth?
- 540 Ma
- continents coming together, moving apart meant climate changing a lot
- snowball conditions- glacial deposits, lots of ic
What is green earth?
- 520 Ma- present
- explosion of diversity
What are the most common elements in the crust?
Oxygen, Silicon, Aluminum (most to least)
What is the most abundant mineral in the crust? What are its 2 parts?
- feldspar (Al, Si, O), an aluminosilicate
- plagioclase feldspar (Ca, Na)- basalt
- alkali feldspar (Na, K)- granite
Feldspar is a what?
aluminosilicate
What is a plagioclase feldspar?
Feldspar made of Calcium and Sodium
Most common mineral in basalt
What is an alkali feldspar?
Feldspar made of potassium and soldium
Most common mineral in granite
Which is easier to decompose and what does it decompose into? Quartz or feldspar?
- feldspar
- Na, K, Ca rich clays, transform into soil
- all of our soil is from weathered crystals of feldspar rocks
- quartz is more resistant to weathering
What is the second most abundant mineral in the crust?
Quartz
Name the silica content and give examples
crust >60% felsic, granite, rhyolite 50-60% intermediate 45-50% mafic, basalt <45% ultramafic, peridotite mantle
Why do we choose to use silica content?
Because as magma rises from mantle to crust, it increases in silica content via incongruent melting.
