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Crystal blades of zincite
CategoryOxide mineral
(repeating unit)
IMA symbolZnc[1]
Strunz classification4.AB.20
Dana classification04.02.02.01
Crystal systemHexagonal
Crystal classDihexagonal pyramidal (6mm)
H-M symbol: (6mm)
Space groupP63mc
ColorOrange, yellow-orange to deep red, red, rarely yellow, rarely green and colorless to white
Crystal habitDisseminated – occurs in small, distinct particles dispersed in matrix.
TwinningOn {0001}
CleavageOn {1010}, perfect; parting on {0001}
Mohs scale hardness4
LusterSubadamantine to resinous
StreakYellowish orange
DiaphaneityTranslucent, transparent in thin fragments
Specific gravity5.64–5.68
Optical propertiesUniaxial (+)
Refractive indexnω = 2.013, nε = 2.029
Birefringenceδ = 0.016

Zincite is the mineral form of zinc oxide (ZnO). Its crystal form is rare in nature; a notable exception to this is at the Franklin and Sterling Hill Mines in New Jersey, an area also famed for its many fluorescent minerals. It has a hexagonal crystal structure and a color that depends on the presence of impurities. The zincite found at the Franklin Furnace is red-colored, mostly due to iron and manganese dopants, and associated with willemite and franklinite.

Microscopic image of Zincite and Franklinite under normal light

Zincite crystals can be grown artificially, and synthetic zincite crystals are available as a by-product of zinc smelting. Synthetic crystals can be colorless or can range in color from dark red, orange, or yellow to light green.

Synthetic zincite crystals

Both natural and synthetic zincite crystals are significant for their early use as semiconductor crystal detectors in the early development of crystal radios before the advent of vacuum tubes. As an early radio detector it was used in conjunction with another mineral, galena, and this device was known as the cat's-whisker detector.

See also[edit]


  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Zincite. Handbook of Mineralogy
  3. ^ Zincite. Mindat

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