Mineralogy

7 crystal systems

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cubic

tetragonal

orthorhombic

OPX

monoclinic

clinoamphiboles, CPX, orthoclase

triclinic

rhombohedral

hexagonal

Qtz

divergent plate boundary

convergent plate boundary

transform plate boundary

layers of the earth

oceanic crust 7-10km

continental crust 25 - 40km

mantle 2,900km

outer core 2,200km

inner core 2,414km

composition of oceanic lithosphere

basaltic rocks - Fe, Mg

mineral

A mineral is a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition

rock

any naturally occurring solid mass or aggregate of minerals

different between a mineral and crystal

Minerals have a naturally formed, organized atomic structure with a specific chemical composition. Crystals for the most part will share these features, however the atoms are arranged in a repeating pattern that results in a crystal lattice, often presenting itself with crystal faces

polymorph

A polymorph is a mineral with the same chemical composition but a different internal structure

binary eutectic with solid solution

solid solution is range between Di and An (end members)

• two different chemical compositions are possible (dependant on T and P)

EX: with exsolution lamellae, the more An end member will form first and then Di end member at a lower T and P

silicate mineral groups

1. orthosilicates

2. pyrosilicates

3. ring silicates

4. single chain silicates (pyroxenes)

5. double chain silicates (amphiboles)

6. sheet silicates

7. framework/tectosilicate/3D

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orthosilicates

simplest silicates which contain discrete SiO₄^4- tetrahedral units

Olivine

pyrosilicate

joining two tetrahedral SiO₄^4- which share one oxygen atom between them

ring silicates

linking three or more tetrahedral SiO₄^4- units

single chain silicates

linked, alternating SiO₄^4- tetrahedra units

Pyroxenes

double chain silicates

chain of ring silicates

Amphiboles

sheet silicates

each SiO₄ tetrahedron shares three oxygen atoms, forming sheets

Micas, Clays

Framework/tectosilicate (3D)

shares all oxygens

Quartz, Feldspars

how are minerals classified

defined/grouped by their common anion/anionic groups

1. silicates

2. sulfides

3. oxides

4. halides

5. carbonates

6. elemental/native metals

7. sulfates

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silicates

anion: SiO₄

sulfides

anion: S₂

metal cation bonded to a sulfide anion

oxides

anion: O

metal cations bonded to oxygen anion

halides

salt anion (F^- or Cl^-)

carbonates

anion: CO₃

Ca or Mg bond to carbonate anion

sulfates

anion: SO₄

metal cation bonds to sulfate anion

why do alkali feldspars show exsolution lamellae

Exsolution lamellae are fine crystals that were dissolved entirely in their host mineral structures at high temperature (e.g., clino- and orthopyroxenes) and/or pressure (e.g., majorite-pyroxenes), but are produced when their host minerals lose the solubility as a result of cooling to low temperatures

why do clays have higher cation coefficients?

Because clay particles are so small, pure clay has at least 1000 times more external surface area than coarse sand. Because clays have a large surface area and negative charges, they can attract and hold positively charged ions

As a result, the cations remain within the soil root zone and are not easily lost through leaching.

composition of continental lithosphere

granitic - Al, Si

composition of mantle

O, Si, Mg

composition of outer core

liquid - Fe, Ni and smaller amounts of Si, O

composition of inner core

solid - Fe, Ni

elemental/native metal

pure mass of a single metal (e.g. copper)