Department of Geological and Environmental Sciences

Dark Colored Minerals with Non-Metallic Lusters, Harder than Glass, no Cleavage

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PHYSICAL PROPERTIES

MINERAL NAME, FORMULA

RED, REDDISH BROWN, BLACK color; equant crystals, often showing 12 to 24 faces; may show parting that may be confused with cleavage; can be massive; H=6.5-7.5.

GARNET,
(Fe,Mg,Ca)3Al2Si3O12

DARK to LIGHT GRAY, but can be any color including purple, pink, yellow, etc. CONCHOIDAL FRACTURE; vitreous luster; H=7; may have crystal faces.

QUARTZ,
SiO2

GREEN, brown, yellow color; vitreous luster; GENERALLY GRANULAR; heavy; H=6.

OLIVINE,
(Mg,Fe)2SiO4