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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
Dolomite CaMgCO3
Calcite CaCO3
• 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
– Halite
– Fluorite
+ halogen
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
Hard –10 diamond
–9 corundum
–8 topax, zircon
–7 quartz
6.5 steel file
–6 feldspar
5.5
glass
or
steel
knife
–5 apatite
–4 fluorite
3.5 copper penny
–3 calcite
2.5 finger nail
–2 gypsum
Soft –1 talc
• 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
Magnetic
– i) HCl acid test: bubbling
on Island
carbonates (calcite, malachite &
azurite)
– ii) double refraction: perfect
crystal of calcite
– iii) magnetic: magnetite
– iv) fluorescent = glows a different
colour under UV light: fluorite
HW
1. start lab 2.1
2. Do 2.1 at home.
 Minerals without names
Minerals with names
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