mineral groups

elements

• 92 naturally occurring

• 8 common in earths crust

which 2 elements are most common

oxygen and silicon

most common minerals are made of…

oxygen, silicon, and a few other elements

native elements

• composed of a single element

• gold, silver, copper, sulphur

• carbon occurs as diamond

mineral groups are classified by…

negative anion or radical

sulfides

• sulfide minerals found in many types of rock

• sulfur + metallic element

• economically important!

oxides- Magnetite (Fe3O4)

• aka lodestone

• spontaneously magnetized

• loses magnetism above Curie temp. (858K)

• historically used in compasses

oxides- Haemetite (Fe2O3)

• not spont. magnetized

• major source of iron ore

• characteristically green + brown/red

oxides- alumina corundum (Al2O3)

• most common crystalline form

• contains traces of Ti, Fe, Cr

• impurities determine colour!

• second hardest mineral after diamond

oxides- uranite

• aka pitchblende

• radioactive

• Athabasca Basin (sask) = major producer

halides

• anion is a halogen

• ex. Halite (NaCl)

• ex. Sylvite (KCl)

silicates

• anion is silica tetrahedra: (SiO4)^4-

• covalent bond between Si and O

• electric charge balanced by cations between the silica tetrahedra

how are silicate metals classified

• geometry of silica tetrahedra

• type of cations

why arent all combos of geometry/ cation type stable

• Fg/Mg cations are smaller than K/Ca/Na ones

what is present in silicates with every geometry of silica tetrahedra

• Al

ex of a single tetrahedra silicate

olivine

ex of a single chain silicate

augite

ex of a double chain silicate

horneblende

examples of sheet silicates

• biotite

• muscovite

examples of 3d framework silicates

• potassium feldspar

• quartz

single tetrahedras, single chains, and double chain silicates form with… and are usually … in colour

• Fe/Mg as cations

• ferromagnesian

• dark

sheet silicates form with…

EITHER Fe/Mg OR K/Ca/Na as cations

3D framework silicates form with… and are usually … in colour

• K/Ca/Na anions

• non ferromagnesian

• light in colour

going from less (MAFIC) to more complex (FELSIC) silicate structures, … increases BUT … decreases

• density increases

• silica content decreases

forsterite

• isolated tet. silicate

• magnesium silicate

• Mg2SiO4

fayalite

• isolated tetrahedra

• iron silicate

• Fe2SiO4

olivine

• isolated tet.

• iron-magnesium silicate

• FeMgSiO4

• between forsterite and fayalite

single chain silicate mineral group example

pyroxene group → ex. augite

double chain silicate mineral group

amphibole → hornblende

mica sheet silicate group

• covalent bonding within the sheet

• ionic bonding between the sheets

• perfect basal cleavage

muscovite- MICA sheet silicate group

• non ferromagnesium silicate

• sheets up to 3×5 m

• used in metallic paint and makeup

biotite- MICA sheet silicate group

• ferromagnesium silicate

• perfect basal cleavage

• black

• used to date rocks

clay sheet silicate group

• sheet silica minerals with water trapped between sheets

• often formed by weathering of minerals like feldspar

kaolinite- CLAY sheet silica group

• forms china clay

serpentine- CLAY sheet silicate group

• formed via metamorphism of basalt

montmorillonite- CLAY sheet silicate group

• forms bentonite

• used in drilling mud

quartz group

• 3D framework silicate

• continuously bonded SiO4

• very abundant in Earths crust

feldspar group

• interlinked tetrahedra of SiO4 and AlO4 anions (neg. charged framework)

• metal cations in voids (K, Na, Ca)

• 2 orthogonal cleavages

• light coloured

• 60% of crust

potassium feldspar

• K-feldspar/ orthoclase

• KAlSi3O8

• no striations

plagioclase feldspar

• if calcium- anorthite

• if sodium- albite

• occurs bc Ca and Na ions are similar in size

• often has striations

carbonate group

• anion is carbonate radical/ polyatomic ion

• found mostly in the sedimentary rocks (limestone, dolostone)

• derived from shells and hard parts of marine organisms

• mostly associated w biomineralization (clams, snails, etc)

examples of carbonates

1. Calcite and Aragonite (CaCO3)

   1. if tropical→ aragonite/ if temperate/cold → calcite

2. dolomite [CaMg(CO3)²]

sulphate group

• sulphate radical in anion (SO4)

• forms in desert from evaporation of water

• can act as a weak layer where faulting localizes

ex. of sulphate group

gypsum (CaSO42H2O)

• when dried/ compressed → anhydrite (CaSO4)

most rock forming minerals are…

• ferromagnesian silicates

• nonferromagnesian silicates

• carbonates

• sulfates

• halides