Composition: Carbon (C)
Crystal system: Cubic
Diaphaneity: Transparent-translucent
Misc: April birthstone; industrial cutting; defining mineral on Mohs scale
Composition: Carbon (C)
Crystal system: Hexagonal
Diaphaneity: Opaque
Misc: Batteries, steelmaking, brake linings, #2 pencils
Composition: Silica, non-hydrated (SiO2)
Crystal system: Trigonal
Diaphaneity: Transparent-translucent
Misc: Electronics, New Age healing practices; February birthstone; defining mineral on Mohs scale
Composition: Magnesium iron silicate ((Fe, Mg)2SiO4)
Crystal system: Orthorhombic
Diaphaneity: Transparent-translucent
Misc: Aluminum casting; August birthstone
Composition: Calcium carbonate (CaCO3)
Crystal system: Trigonal
Diaphaneity: Transparent-translucent
Misc: Sculpture, Viking navigation, WWII gun sights; defining mineral on Mohs scale
Composition: Magnesium silicate, hydrated (Mg3Si4O10(OH)2)
Crystal system: Monoclinic or triclinic
Diaphaneity: Translucent
Misc: Cosmetics, baby powder, paper making, solid lubricant; defining mineral on Mohs scale
Composition: Calcium fluoride (CaF2)
Crystal system: Isometric
Diaphaneity: Transparent-translucent
Misc: Source of hydrogen fluoride; defining mineral on Mohs scale
Composition: Calcium sulfate dihydrate (CaSO4·2H2O)
Crystal system: Monoclinic
Diaphaneity: Transparent-translucent
Misc: Construction, fertilizer, plaster, tofu coagulant; defining mineral on Mohs scale
Composition: Aluminum oxide (Al2O3)
Crystal system: Trigonal
Diaphaneity: Transparent-translucent
Misc: July birthstone; scratch-resistant optics, laser components; defining mineral on Mohs scale
Composition: Beryllium aluminum silicate (Be3Al2Si6O18)
Crystal system: Hexagonal
Diaphaneity: Transparent to opaque
Misc: May birthstone
Composition: Silica, hydrated (SiO2 nH2O)
Crystal system: Amorphous
Diaphaneity: Opaque to transparent
Misc: October birthstone
Composition: Phosphate of copper and aluminum, hydrated (CuAl6 (PO4) 4 (OH) 8·4H2O)
Crystal system: Triclinic
Diaphaneity: Opaque
Misc: Gemstone whose name indicates its supposedly Turkish origin
Composition: Beryllium aluminate (BeAl2O4)
Crystal system: Orthorhombic
Diaphaneity: Transparent-translucent
Misc: Gemstone shaped as a domed cabochon to highlight its “eye”
Composition: Sodium potassium aluminum silicate ((Na, K)AlSi3O8)
Crystal system: Monoclinic and triclinic
Diaphaneity: Transparent-translucent
Misc: June birthstone; object in a Wilkie Collins novel
Composition: Lead sulfide (PbS)
Crystal system: Cubic
Diaphaneity: Opaque
Misc: Kohl and cosmetics, ceramic glaze; official state mineral of Kansas, Missouri, and Wisconsin
Composition: Ferrous disulfide (FeS2)
Crystal system: Cubic
Diaphaneity: Opaque
Misc: Also known as fools’ gold
Composition: Copper ferrous sulfide (CuFeS2)
Crystal system: Cubic
Diaphaneity: Opaque
Misc: Soft mineral often confused with pyrite; most abundant copper ore mineral
Composition: Ferrous-ferric oxide (Fe2+Fe3+2O4)
Crystal system: Isometric
Diaphaneity: Opaque
Misc: What lodestones are made of
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