GEOS - 3. Minerals
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What are the four most common elements on EartH?
- Iron 35%
- Oxygen 30%
- Silicon 15%
- Magnesium 13%
What are the 3 most common elements in the crust?
- Oxygen 46%
- Silicon 28%
- aluminum 8%
What is a rock?
Attached assemblage of minerals
What is the term for the study of rocks?
Natural, inorganic solid which characteristic chemical compositions and internal structure; crystalline substances
What is concrete not a rock?
It is a manmade material
What is a crystal?
Repeated regular arrangement of specific elements in a solid; thus symmetry is built in
What are the methods used to identify minerals?
Hand sample, thin section, geochemistry, geophysics
How does the thin section method of identifying minerals work?
Slice the rock into a thin section. Put it under a microscope and shine a light through it - this can be used to identify minerals by optical properties
How does the geochemistry method of identifying minerals work?
X-ray diffraction, looking at the chemistry of the rock scale, mineral scale, and atomic scale
How does the geophysics method of identifying minerals work?
Look at sounds speeds through rocks
What are silicates made predominantly out of?
Silicon & oxygen
How are silicates constructed?
In an octahedron or tetrahedron form; in between negatively charged silicate groups are positively charged cations
What is the difference between silicate octohedron and silicate tetrahedron?
Octahedra are sharing corners; most of the rocks we will touch are tetrahedrons, which can stand alone; tetrahedron are bonded together in sheets or in 3D frameworks
Silicates make up greater than ___ percent of the planet.
What are silicates used for?
Many industrial rocks and minerals, many ores, clay, and gems
- Magnesium silicate
- Octahedron structure
- Makes up most of the lower mantle
- Most common mineral in earth
- Is exceedingly rare on the surface of the planet
- Very dense
What is the trend between distance from mantle and the presence of iron and magnesium?
As you get more and more away from the mantle, you get less and less iron and magnesium
- An iron magnesium silicate
- 65+% of the upper part of the mantle
- Low pressure mineral
- Also seen in the crust but is it not in the top five.
- Iron magnesium silicate
- Can contain calcium and aluminum
- Common in upper mantle and ocean crust
- Forms chains, a little more of a complex structure than tetrahedron
- Common in upper mantle
- Has various elements: Fe, Mg, Al, Ca, Cr
- Has a complex 3D framework
- Makes up ~10% of upper mantle
- A minor component of the crust
- In the crust
- Has water in the mineral
- Iron magnesium silicate; include OH-
- May include aluminum, calcium, Na
- Amphiboles include hornblende
- Double chain structure
- Have aluminum and OH-
- Can have Fe, MG, K, Ca, Na
- Sheet silicates
- A huge family of minerals
- Also hydrated like micas
- Must have Aluminum and OH-
- May have K, Na, Ca, Mg
- Comes from breaking down minerals w/ water (weathering)
- Most common mineral group at Earth's surface
- Include Al
- No water built into them
- Most common mineral in both the ocean crust and continental crust
- Do not exist in the mantle
- Have a more 3D framework
- Nothing but silicate
- Fairly common in the continents but not so much in the ocean
- Common on earth's surface bc it doesn't break down under earth and water
- Sand is usually made of this mineral
- 3D framework
- Two oxygen ions for every silicon ion in the structure
What are carbonates, sulphates, and phosphates used for?
Chemicals, fertilizers, industrial rocks (plaster)
- Common in upper crust
- found in shells and limestone
- Water soluble; found in caves
- Plaster of Paris drywall
- Biggest crystals we've ever seen are gypsum in New Mexico
Where can apatite be found?
Bones and fertilizer
What is the most common cation in oxides, hydroxides, and sulphides?
What is galena used for?
What are oxides, hydroxides, and sulphides used for?
- More common sulfide
- Aka fool's gold
- Not a good iron mineral; no economic value
- Looks cubic, unlike real gold
What are halides used for?
Chemicals (salts), fertilizer (potassium)
What is halite more commonly known as?
- Table salt
- We get most of it not by evaporating salt water, but from mining (mining is cheaper)
What is asbestos used for?
- Insulation, fireproof
- A lot of people who work with these end up with this in their lungs --> dying
Discuss toxicity, hazards, regulation of asbestos
- Removal costs billions of dollars
- Chrysotile = 95% asbestos use, the least toxic
- Risk primarily in high concentrations over a long time
- It is only a concern for those who work with asbestos - mining, construction, renovations, etc. (occupational exposure)
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