Geology 12

Presents

Mineralogy• Minerals:

1. Naturally occurring = not man made (but some can be)

2. Inorganic

3. Crystalline solid

a) cubic (dice) ex: halite, galena, pyrite

b) dodacahedron (12 sides) ex: garnet

c) octagonal (2 pyramids, base to base) ex: diamond

d) prism terminated by a pyramid ex: quartz

4. Narrowly defined chemical composition

a) native elements: Au (gold), C (grpahite, diamond), Pt (platinum), Ag (silver)

b) compounds: SiO2 (quartz), NaCl (halite = salt)

*sometimes some elements can substitute within the same mineral.

2 way ex; biotite K (Mg, Fe)3Al Si3O10(OH)2

• 3 way Siderite FeCaCO3

Calcite CaCO3Dolomite CaMgCO3

• 3500 minerals but only about 24 are common

• Number of minerals dependent on:– Some combinations of elements are impossible– Only 8 elements make up the bulk of the Earth’s

crust.– REMEMBER: O Si Al Fe (4 most common

1st 4th elements)

• Minerals are divided into groups.

A) silicates: contain Si & O– Quartz, – feldspars, – muscovite, – biotite, mica family– Chlorite– Talc– Augite– Hornblende– Garnet– Asbestos– Olivine

B) Oxides: an element + O (metallic mineral)

– hematite (looks like blood)

– limonite– magnetite

C) Sulphides: ion+ + sulfur (metallic mineral)

– pyrite “fools’ gold”– chalcopyrite– pyrrhotite– galena– sphalerite– molybdenite “flakey chick”– bornite “peacock rock”

• D) Carbonates +CO3

– Calcite– Malachite– Azurite

E) Sulphates + SO4

– gypsum

• F) Native Elements (metallic mineral)– Gold– Graphite

G) Halides + halogen– Halite– Fluorite

H) Phosphates + phosphate– apatite

• 5. Characteristic physical properties (how we identify them)– A) colour: non-fe-mg are lighter in colour– B) streak = colour of dust after dragging it on

a tile; silicates light, metallics dark– C) Luster: way it reflects light, usually metallic

or non-metallic

• D: Crystal form– Crystals/prismatic

– Granular

– Fibrous

– Massive

– Tabular

– Stubby

– E) Cleavage: tendency to break along a flat plane ie. 1 excellent, 3 poor, etc.

• Fracture: breakage along an irregular surface

–i.e. concoidal (glass), hackly, etc.

• F) Hardness Moh’s Scale

–10 diamond–9 corundum–8 topax, zircon–7 quartz–6 feldspar–5 apatite–4 fluorite–3 calcite–2 gypsum–1 talc

6.5 steel file

5.5 glass or steel knife

3.5 copper penny2.5 finger nail

Hard

Soft

• G) Specific Gravity = density= density compared to water (1)

Average is about 3

Silicates: 2.7 – 4

Metallics: most >5

iron is 5.5, lead is 8, gold is 19

Heavy HD Ugg!

• H) other properties– i) HCl acid test: bubbling on

carbonates (calcite, malachite & azurite)

– ii) double refraction: perfect crystal of calcite

– iii) magnetic: magnetite– iv) fluorescent = glows a different

colour under UV light: fluorite

Magnetic Island

HWHW

1. start lab 2.11. start lab 2.1

2. Do 2.1 at home. 2. Do 2.1 at home.

Minerals without namesMinerals without names

Minerals with names

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