Rock forming minerals

How to Know Minerals
Chapter 4 Earth Science Book
read pages 46-57
restate & answer Topic Questions 1-9
practice the 30 lab mineral samples


Topic 1:

Page 47 Earth Textbook

Rock-Forming Minerals

common minerals that make up the Earth’s crust

* over 2000 minerals known
* most are silicates (Si + O + metals)
* not always large crystals
* mineralogy is the study of minerals
and their properties


Topic 2:

Page 47-48 Earth Textbook

Identification by
Inspection
simple observations made by looking
*Color
*Luster

*Crystal System (shape)


Topic 2:

Page 47 Earth Textbook

Color
* first, most easily observed
* least useful when identifying minerals
1. impurities change mineral’s colors
2. mineral’s colors are similar
3. colors change/react in air


Topic 2:

Page 47 Earth Textbook

Luster

the way a mineral shines
* Metallic Luster
* Nonmetallic Luster


Topic 2:

Page 47 Earth Textbook

Metallic Luster
*shines like polished metal
*(galena, pyrite, chalcopyrite)


Topic 2:

Page 47-48 Earth Textbook

Nonmetallic Luster
*vitreous – shining glass (quartz)
*pearly – like a pearl (mica)
*resinous – like wax (sphalerite)
*greasy, oily – (talc & graphite)
*dull, earthy – (kaolinite, limonite)
*brilliant, adamentine – (diamond)


Topic 2:

Page 47-48 Earth Textbook

Crystal System (shape)

*cubic – all 90º, all lengths equal
*orthorhombic – all 90º, no lengths equal
*tetragonal – all 90º, some lengths equal
*triclinic – none @ 90º
*monoclinic – some @ 90º
*hexagonal – 3 axes @ 60º

Topic 3:

Page 48-50 Earth Textbook

Identification by
Simple Tests
*Streak
*Fracture or Cleavage
*Hardness


Topic 3:

Page 48 Earth Textbook

Streak
the color of a mineral’s powder
* rub mineral on unglazed white tile
metallic - streak dark as mineral
nonmetallic - streak colorless to light


Topic 3:

Page 49 Earth Textbook

Cleavage
minerals split along flat surfaces

1 direction – micas, gypsum, talc
2 directions – feldspars, hornblende
3 directions – galena, halite, calcite


Topic 3:

Page 49 Earth Textbook

Fracture

minerals break along non-cleavage surfaces

•concoidal fractures – shell-like fracture
•fiberous or splintery – jagged and sharp
•uneven or irregular – rough surface


Topic 3:

Page 49-50 Earth Textbook

Hardness
minerals resistance to being scratched
*Mohs’ Hardness Scale – page 50 in text
•minerals ranked on a scale of 1 to 10
•need fingernail, copper, steel, glass, topaz
•1 softest (talc), 7 hardest common (quartz)
and 10 is the hardest of all (diamond)

Topic 4:

Page 50 Earth Textbook

Specific Gravity

the ratio of the mass of a mineral to the mass of
an equal volume of water

•specific gravity = mass of sample in air
mass lost in water
•nonmetals - less than 4
•metals - above 5


Topic 5:

Page 51 Earth Textbook

Acid Test

weak acid will release bubbles of CO2
*calcium carbonate fizzes in acid (HCl)
*calcite is calcium carbonate, CaCo3
*dolomite - CaMg(CO3) must be powdered
*malachite & azurite are copper carbonates
*limestone & marble calcite

Topic 6:

Page 51 Earth Textbook

Special Properties

•taste – halite is salty
•magnetic - magnetite
•double diffraction – calcite/Iceland par
splits images into 2
•flourescence – glows under ultraviolet
light, fluorite, sphalerite, willemite
•phosphorescence – glows even after
ultraviolet off


Topic 7:

Page 53-54 Earth Textbook

Silicates
made with silica tetrahedrons (light colored)
a) quartz
b) feldspars: orthoclase, plageoclase
c) micas: muscovite, biotite(black)
d) talc


Topic 7:

Page 54-55 Earth Textbook

Ferromagnesian Silicates

silicates with iron and magnesium (darker)
e) amphiboles: horneblende
f) pyroxenes: augite
g) olivine
h) garnets
i) kaolinite


Topic 8:

Page 55-56 Earth Textbook

Carbonates

made with carbonate group –CO3
*Calcium Carbonates
•calcite(Iceland spar), dolomite
*Copper Carbonates
•malachite, azurite


Topic 9:

Page 56-57 Earth Textbook

Oxides

a metal combines with oxygen
*Iron Oxides
•hematite (reddish-brown streak)
•limonite (yellow-brown streak)
•magnetite
*Aluminum Oxides
•corundum
•bauxite


Topic 9:

Page 56-57 Earth Textbook

Sulfides

a metal combines with sulfur
•galena
•pyrite
•chalcopyrite
•sphalerite


How to Know Minerals
Chapter 4 Earth Science Book
read pages 46-57
restate & answer Topic Questions 1-9
practice the 30 lab mineral samples