Rock forming minerals

How to Know MineralsChapter 4 Earth Science Book read pages 46-57 restate & answer Topic Questions 1-9 practice the 30 lab mineral samples... common minerals that make up the Earth’s cru

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

common minerals that make up the Earth’s crustRock-Forming Minerals

* over 2000 minerals known

* most are silicates (Si + O + metals)

* not always large crystals

* mineralogy is the study of minerals

simple observations made by looking

* 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

Metallic Luster

*shines like polished metal

*(galena, pyrite, chalcopyrite)

Nonmetallic Luster

*vitreous – shining glass (quartz)

*pearly – like a pearl (mica)

*greasy, oily – (talc & graphite)

*resinous – like wax (sphalerite)

*dull, earthy – (kaolinite, limonite)

*brilliant, adamentine – (diamond)

Crystal System (shape)

*cubic – all 90º, all lengths equal

*orthorhombic – all 90º, no lengths equal

*triclinic – none @ 90º

*tetragonal – all 90º, some lengths equal

*monoclinic – some @ 90º

*hexagonal – 3 axes @ 60º

* rub mineral on unglazed white tile

metallic - streak dark as mineral

nonmetallic - streak colorless to light

the color of a mineral’s powder

1 direction – micas, gypsum, talc

2 directions – feldspars, hornblende

3 directions – galena, halite, calcite

minerals split along flat surfaces

•concoidal fractures – shell-like fracture

•fiberous or splintery – jagged and sharp

•uneven or irregular – rough surface

minerals break along non-cleavage surfaces

*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)

minerals resistance to being scratched

the ratio of the mass of a mineral to the mass of

an equal volume of water

Specific Gravity

•specific gravity = mass of sample in air mass lost in water

•nonmetals - less than 4

weak acid will release bubbles of COAcid Test 2

*calcite is calcium carbonate, CaCo3

*dolomite - CaMg(CO3) must be powdered

*malachite & azurite are copper carbonates

*calcium carbonate fizzes in acid (HCl)

*limestone & marble calcite

Special Properties

•taste – halite is salty

•magnetic - magnetite

•flourescence – glows under ultraviolet

light, fluorite, sphalerite, willemite

•phosphorescence – glows even after

•double diffraction – calcite/Iceland par

splits images into 2

made with silica tetrahedrons (light colored)Silicates

a) quartzb) feldspars: orthoclase, plageoclasec) micas: muscovite, biotite(black)d) talc

silicates with iron and magnesium (darker)Ferromagnesian Silicates

e) amphiboles: horneblendef) pyroxenes: augite

g) olivineh) garnetsi) kaolinite

made with carbonate group –COCarbonates 3

•calcite(Iceland spar), dolomite

•malachite, azurite

*Calcium Carbonates

*Copper Carbonates

a metal combines with oxygenOxides

•hematite (reddish-brown streak)

•limonite (yellow-brown streak)

•magnetite

•corundum

*Iron Oxides

*Aluminum Oxides

a metal combines with sulfurSulfides

•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