Spinel Group Flashcards

1
Q

MgAl2O4

A

Spinel

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2
Q

Isometric. Commonly in octahedral crystals or in twinned octahedrons (spinel twins). Dodecahedron may be present as small truncations but other forms are rare.

A

Spinel

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3
Q

Hardness of spinel?

A

8

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4
Q

Specific gravity of spinel?

A

3.5-4.1

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5
Q

What is the usual color of spinel?

A

Various shades of white, red, lavender, blue, green, brown, and black.

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6
Q

A common high-temperature mineral occurring in contact-metamorphosed limestones and metamorphic rocks poor in SiO2. Metamorphic assemblages may contain phlogopite, pyrrhotite, and graphite.

A

Spinel

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7
Q

Fe3O4

A

Magnetite

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8
Q

Isometric. Frequently in octahedral crystals, more rarely in dodecahedrons. Other forms rare.

A

Magnetite

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9
Q

What is the cleavage of magnetite?

A

None. Octahedral parting in some specimens.

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10
Q

What is the hardness of magnetite?

A

6

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11
Q

What is the specific gravity of magnetite?

A

5.18

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12
Q

What is the usual color of magnetite?

A

Iron black. Luster metallic.

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13
Q

Magnetite may act as a natural magnet known as ______.

A

lodestone

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14
Q

Common mineral found disseminated as an accessory in most igneous rocks. In some igneous rock types magnetite may be the chief constituent of the rock and may form large ore zones; these are commonly titaniferous.

A

occurrence of magnetite

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15
Q

Magnetite may be closely intergrown with corundum, forming ______.

A

emery

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16
Q

FeCr2O4

A

Chromite

17
Q

Isometric, with octahedral habit, but crystals rare. Commonly massive, granular to compact.

A

crystal form of chromite

18
Q

What is the hardness of chromite?

A

5 1/2

19
Q

What is the specific gravity of chromite?

A

4.6

20
Q

What is the usual color of chromite?

A

Iron black to brownish black

21
Q

A common constituent of peridotites, of other ultrabasic rocks, and of serpentine derived from them. Associated with olivine, serpentine, and corundum.

A

Chromite