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) 3 Al Si 3 O 10 (OH) 2

3 way Siderite FeCaCO 3 Calcite CaCO 3 Dolomite CaMgCO 3

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 1 st 4 th 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 +CO 3 –Calcite –Malachite –Azurite E) Sulphates + SO 4 –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 penny 2.5 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

HW 1. start lab Do 2.1 at home.  Minerals without names Minerals without namesMinerals without names  Minerals with names Minerals with names Minerals with names Go to beginning