EOSC210 Rocks

Magnetite (Iron Ore)

Magnetite (Iron Ore)

Fe3O4 ● Strongly magnetic ● High specific gravity ● Lustre: Metallic dull ● Colour: Black ● Streak: Black ● Hardness: 5.5-6

Galena (Lead Ore)

PbS ● Perfect 3 way cleavage at 90 degrees ● High specific gravity ● Habit: Cubic shape ● Lustre: Metallic bright ● Colour: Greyish blue ● Streak: Greyish black ● Hardness: 2.5

Hematite (Iron Ore)

Fe2O3 ● Lustre: Metallic/ Earthy/ Dull ● Colour: Reddish grey/ Black/Blackish red ● Streak: Reddish brown ● Hardness: 6.5

Pyrite (Fool's Gold, not Economic)

FeS2 ● Habit: Cubic, isometric (Moregeometric than Chalcopyrite) ● Lustre: Metallic ● Colour: Pale brass yellow ● Streak: Greenish black ● Hardness: 6.5

Chalropyrite (Copper Ore)

CuFeS2 ● Lustre: Metallic ● Colour: Bright brass yellow (sometimes golden) ● Streak: Greenish black ● Hardness: 3.5

Calcite

CaCO3 ● Strong reaction with acid ● Perfect 3 way cleavage at 120/60 degrees ● Lustre: Vitreous/ Glassy ● Colour: Colourless/ White/ Yellow (could also be pink and brown sometimes) ● Streak: White ● Hardness: 3

Pyroxene (Augite variety)

(Ca, Na) (Mg, Fe, Al) (Si, Al)2O6 ● Perfect 2 way cleavage at 90 degrees ● Lustre: Vitreous ● Colour: Brown green, Green, Light brown, Dark brown, Black ● Streak: Greenish white ● Hardness: 5-6.5

Plagioclase (Albite variety - Na-rich Feldspar)

NaAlSi3O8 ● Perfect 2 way cleavage at 90 degrees ● Polysynthetic twinning/ Albite twinning ● Lustre: Vitreous/ Glassy ● Colour: White ● Streak: White ● Hardness: 5-6.5

Quartz (massive or crystalline)

SiO2 ● Prismatic ● Conchoidal fracture ● Lustre: Vitreous/ Glassy ● Colour: Variable ● Streak: White ● Hardness: 7

Orthoclase (K-rich Feldspar)

(K, Na)AlSi3O8 ● Perfect 2 way cleavage at 90 degrees ● Perthitic texture ● Carlsbad twinning ● Lustre: Vitreous/ Glassy ● Colour: Variable but Pink/ Colourless/ White most common ● Streak: White ● Hardness: 6

Garnet (crystal)

(Ca, Mg, Fe, Mn)3 Al2Si3O12 ● Habit: Dodecahedron, isometric ● Lustre: Vitreous/ Resinous ● Colour: Reddish brown ● Streak: White ● Hardness: 7-8

Amphibole (Hornblende variety)

(Na,K)0-1 (Ca, Na, Mg, Fe)2 (Mg, Fe, Al)5 (Si, Al)8O22 (OH)2 ● 60/120 degree cleavage ● Lustre: Vitreous ● Colour: Black ● Streak: White ● Hardness: 5-6

Olivine

(Mg2Fe)2SiO4 ● Conchoidal fracture ● Lustre: Vitreous/ Glassy ● Colour: Yellowish green, Olive green, Greenish black (sometimes reddish brown) ● Streak: White ● Hardness: 6.5-7

Muscovite (White/Clear Mica)

KAl2 (AlSi3O10) (F, Cl, OH)2 ● Perfect one way (basal cleavage) ● Lustre: Vitreous/ Pearly ● Colour: White, Gray, Silver white ● Streak: White ● Hardness: 2.5

Biotite Mica (Black Mica)

K(Mg, Fe)3 (AlSi3O10) (F, Cl, OH)2 ● Perfect one way (basal cleavage) ● Lustre: Vitreous/ Pearly ● Colour: Black, Dark brown, Blackish brown ● Streak: Grey ● Hardness: 2.5-3

Gypsum

CaSO4 • 2H2O ● Lustre: Pearly ● Colour: White, Colorless, Yellowish white ● Streak: White ● Hardness: 2

Staurolite

Indicates high grade metamorphism ● Penetration twins (Cross twins) ● Lustre: Vitreous/ Dull ● Colour: Brownish yellow, Brownish black, Yellow brown, Dark brown, Reddish brown. ● Streak: Grey ● Hardness: 7-7.5

Kyanite

Indicates high grade metamorphism (equal or greater than Staurolite) ● Habit: Blade-like ● Lustre: Vitreous/ Pearly ● Colour: Commonly blue (sometimes white, grey, green, black) ● Streak: Grey ● Hardness: Parallel = 4.4.5 Perpendicular = 6.5

Gabbro

● Composition: Mafic ● Formation: Intrusive ● Texture: Crystalline, Phaneritic ● Minerals: Calcium rich: pyroxene; olivine; plagioclase feldspar; amphibole

Granite

● Composition: Felsic ● Formation: Intrusive ● Texture: Crystalline, Phaneritic ● Minerals: Sodium rich: quartz; potassium feldspar; biotite; amphibole

Obsidian

● Composition: Mafic ● Formation: Extrusive ● Texture: Non-crystalline, Glassy ● Conchoidal fracture

Pumice

● Composition: Mafic ● Formation: Extrusive ● Texture: Non-crystalline, Glassy ● Light weight ● Very porous

Basalt

● Composition: Mafic ● Formation: Extrusive ● Texture: Crystalline, Aphanitic ● Minerals: Calcium rich: pyroxene; olivine; plagioclase feldspar; amphibole

Ash Tuff

● Composition: Felsic ● Formation: Extrusive ● Texture: Noncrystalline, Fragmental/pyroclastic

Porphyritic Andesite

● Composition: Mafic ● Formation: Extrusive ● Texture: Crystalline, Porphyritic ● Minerals: Pyroxene; plagioclase feldspar; amphibole ● 2 stage cooling

Slate

● Sheet-like texture (Slatey) ● Low grade ● Fine-grained ● Composition: Micas, quartz ● Protolith: Mudstone/shale ● Formation: Regional/dynamic

Schist

● Schistosity ● Medium grade ● Medium coarse-grained ● Composition: Micas, kyanite, garnet ● Protolith: Mudstone/shale ● Formation: Regional/dynamic

Gneiss

● Gneissosity (Compositional banding) ● High grade ● Medium coarse-grained ● Composition: Quartz, feldspar ● Protolith: Granite and mudstone/shale ● Formation: Regional/dynamic

Marble

● Low-high grade ● Reacts strongly to acid ● Hardness: 3 ● Composition: Calcite, dolomite ● Protolith: Limestone ● Formation: Contact

Quartzite

● Medium-high grade ● No reaction to acid ● Hardness: 7 ● Composition: Quartz ● Protolith: Sandstone ● Formation: Contact

Shale

● Very fine grain ● Well-sorted ● Rounded grains ● Environment: River, lake, swamp; less likely in tidal flat or lagoon

Lithic Sandstone/Greywacke

● >15% fine grained matrix like clay ● Composed of mostly rock fragments ● Fine-grained ● Well sorted/ Poor graded ● Angular, low sphericity ● Environment: River (High energy settings)

Arkosic Sandstone - Feldspar Rich

● Coarse-grained ● Poorly-sorted ● Poorly rounded, low sphericity ● Commonly reddish in colour ● Environment: River (High energy settings)

Red Sandstone (rich iron oxides like hematite)

● Coarse-grained ● Well-sorted ● Rounded, high sphericity ● Environment: Desert (red), beach, river

Conglomerate

● Coarse-grained ● Poorly sorted ● Rounded, high sphericity ● Grains of varying composition ● Environment: River (Medium to high energy setting)

Breccia

● Coarse-grained ● Poorly sorted ● Angular, low sphericity ● Grains of varying composition ● Environment: River (High energy setting)

Chert

● Conchoidal fracture ● Very fine-grained, undistinguishable grains ● Contains mainly quartz ● Environment: Deep marine

Microcrystalline Limestone

● Reacts strongly with acid ● Composed of Calcite ● Medium to coarse-grained ● May contain fossils ● Environment: Shallow marine

Evaporite

● Composed of Halite/table salt or Gypsum ● Medium to coarse-grained ● Environment: Tide pools, lagoon

Coal

● Composed of organic material ● Environment: Swamp