EOSC210 Rocks

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