Oxides and Halides

Bauxite

• AlO(OH) but thats just the aluminum part?

• Hardness: 1-3

• Luster: dull, earthy

• Streak: white

• Color: white, gray, or yellow/brown/orange/red rusty colors

• Cleavage/Fracture: uneven fracture

• SG: 2-2.5

• Magnetism: none

• Opacity: opaque

• Other: actually a rock? usually pisolitic

Corundum

• Al₂O₃

• Hardness: 9

• Luster: adamantine to vitreous

• Streak: none/colorless

• Color: colorless, gray, brown, any color of the rainbow

• Cleavage/Fracture: conchoidal to uneven frac

• SG: 3.95-4.1

• Magnetism: none

• Opacity: transparent, translucent, or opaque

• Other: trigonal, forms hexagonal prisms or rhombohedral

Goethite

• FeO(OH)

• Hardness: 5-5.5

• Luster: adamantine to dull

• Streak: brown to yellow to orange

• Color: brown or black, could be slightly yellowish or reddish

• Cleavage/Fracture: 2 cleav, uneven to splintery frac

• SG: 3-3-4.3

• Magnetism: slightly

• Opacity: opaque to sub-translucent

• Other: orthorhombic, radial acicular, botryoidal, massive

Hematite

• Fe₂O₃

• Hardness: 5.5-5.6

• Luster: metallic, reflective

• Streak: bright to dark red

• Color: gray, rust-red in massive/fine-grained, gray to black in crystalline

• Cleavage/Fracture: uneven frac

• SG: 5.26

• Magnetism: none

• Other: trigonal, lots of habits, botryoidal, rosettes, platy, tabular

Ilmenite

• FeTiO₃

• Hardness: 5-6

• Luster: metallic to submetallic

• Streak: black

• Color: black, gray, some brown

• Cleavage/Fracture: conchoidal frac

• SG: 4.7-4.8

• Magnetism: weakly magnetic

• Opacity: opaque

• Other: trigonal, granular to massive

Pyrolusite

• MnO₂

• Hardness: 6-6.5 but 2 when massive

• Luster: metallic to dull

• Streak: black to bluish black

• Color: dark black to gray, sometimes bluish

• Cleavage/Fracture: 1 cleav, uneven frac

• SG: 4.4-5

• Magnetism: none

• Opacity: opaque

• Other: tetragonal, granular massive, botryoidal, acicular

Limonite

• FeO(OH) · nH₂O

• Hardness: 4-5.5

• Luster: dull/earthy

• Streak: yellowish brown

• Color: shades of brown and yellow

• Cleavage/Fracture: uneven frac

• SG: 2.9-4.3

• Magnetism: none

• Opacity: opaque

• Other: fine-grained, powdery

Rutile

• TiO₂

• Hardness: 6-6.5

• Luster: adamantine to metallic

• Streak: bright to dark red, gray

• Color: brown, reddish brown, shades of red and yellow, grayish black

• Cleavage/Fracture: 1.5 cleavs, uneven frac

• SG: 4.23

• Magnetism: none

• Opacity: opaque, transparent if thin

• Other: tetragonal, prismatic, elongated and striated

Chromite

• (Fe, Mg)Cr₂O₄

• Hardness: 5.5

• Luster: dull to resinous to metallic

• Streak: brown

• Color: black to brown

• Cleavage/Fracture: uneven fracture

• SG: 4.5-4.8

• Magnetism: none

• Opacity: translucent to opaque

• Other: spinel group, isometric, usually massive to granular (octahedrons?)

Magnetite

• Fe²⁺Fe₂³⁺O₄

• Hardness: 5.5-6.5

• Luster: metallic

• Streak: black

• Color: black, gray, maybe brown

• Cleavage/Fracture: uneven frac

• SG: 5.18

• Magnetism: yes, strong

• Opacity: opaque

• Other: spinel group, isometric, octahedral or fine granular, massive

Gahnite

• ZnAl₂O₄

• Hardness: 7.5-8

• Luster: vitreous

• Streak: grey

• Color: dark green, bluish green, yellow, brown

• Cleavage/Fracture: conchoidal to uneven frac

• SG: 4.38-4.6

• Magnetism: none

• Opacity: translucent to almost opaque

• Other: spinel group, cubic, octahedra, massive to granular

Fluorite

• CaF₂

• Hardness: 4

• Luster: vitreous

• Streak: white

• Color: colorless or any color of the rainbow

• Cleavage/Fracture: octahedral, 4 cleavs

• SG: 3.2

• Magnetism: none

• Opacity: transparent to translucent

• Other: isometric, coarse crystals

Halite

• NaCl

• Hardness: 2-2.5

• Luster: viterous

• Streak: white

• Color: colorless/white, with impurities yellow, gray, black, brown, red

• Cleavage/Fracture: 3 cleavs, conchoidal frac

• SG: 2.17

• Magnetism: none

• Opacity: transparent to translucent

• Other: cubic or granular, cubic

Sylvite

• KCl

• Hardness: 2

• Luster: vitreous

• Streak: white

• Color: colorless/white, pale gray/blue, yellowish red

• Cleavage/Fracture: three cleavs, uneven frac

• SG: 1.993

• Magnetism: none

• Opacity: transparent to translucent

• Other: isometric, cubes and octahedra, columnar, massive