Zincite

Big Photo

Octagon zincite
5.06 carats
© Rarestone.com

Zincite, in the gem world, is primarily a man-made material, being produced by zinc smelters in Poland as a by-product of zinc metal extraction from ore. The crystals are said to have formed in furnace smoke stacks, and come to market occasionally when these smoke stacks are cleaned or maintained.

Zincite is also known as a natural mineral (in particular, fine specimens have been found at the Franklin/Sterling Hill deposit in New Jersey), but these are generally not gem quality, although they are occasionally cut as opaque orange-red to very dark red cabochons, which can reach 295 carats or more in weight. (Keep in mind that the high density means that gems will be smaller size than one would expect from the carat weight.)

The name is derived from its zinc content.

Zincite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 

Zincite Gemstones by Size

This table shows distribution of Zincite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.14 cts
Heaviest:19.14 cts
Average:12.21 cts
Total photos:8
Do you have a larger Zincite? Why not upload a photo?
0.14ct to 2.04ct2.04ct to 3.94ct3.94ct to 5.84ct5.84ct to 7.74ct7.74ct to 9.64ct9.64ct to 11.54ct11.54ct to 13.44ct13.44ct to 15.34ct15.34ct to 17.24ct17.24ct to 19.14ct
General Information
Chemical Formula
(Zn,Mn
2+
 
)O
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Zincite
Mohs Hardness4
Michael O’Donoghue, Gems, Sixth Edition (2006) NaturalMore from other references
Specific Gravity5.50 to 5.90
Robert C. Kammerling, The Journal of Gemmology (1995)
More from other references
TenacityBrittle
Gemdat.org, Management Team (2012)
Cleavage QualityPerfect
Arthur Thomas, Gemstones (2009)
FractureSub-Conchoidal
Arthur Thomas, Gemstones (2009)
Optical Properties of Zincite
Refractive Index2.013 to 2.029
Michael O’Donoghue, Gems, Sixth Edition (2006) NaturalMore from other references
Optical CharacterUniaxial
Robert C. Kammerling, The Journal of Gemmology (1995)
More from other references
Birefringence0.016
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
PleochroismVery weak, in two tones of body colour
Robert C. Kammerling, The Journal of Gemmology (1995)
DispersionLow
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Medium-light yellow, medium orange, medium-dark reddish-orange
Robert C. Kammerling, The Journal of Gemmology (1995)
More from other references
Colour (Chelsea Filter)Yellow stone: no reaction (appears yellowish-green). Orange stone: weak pink. Reddish-orange stone: moderate red
Robert C. Kammerling, The Journal of Gemmology (1995)
TransparencyTransparent
Robert C. Kammerling, The Journal of Gemmology (1995)
More from other references
LustreSubadamantine
Robert C. Kammerling, The Journal of Gemmology (1995)
Fluorescence & other light emissions
Fluorescence (General)LW > SW; both universely propotional to depth of body colour
Robert C. Kammerling, The Journal of Gemmology (1995)
Fluorescence (Short Wave UV)Inert to very weak to moderate, yellow to orange
Robert C. Kammerling, The Journal of Gemmology (1995)
Fluorescence (Long-Wave UV)Very weak to moderate, yellow to yellow-orange
Robert C. Kammerling, The Journal of Gemmology (1995)
Crystallography of Zincite
Crystal SystemHexagonal
Arthur Thomas, Gemstones (2009)
HabitUsually massive, foliated; also compact granular, and in rounded irregular masses.
Gemdat.org, Management Team (2012)
More from other references
Geological Environment
Where found:Occurs as a primary mineral in metamorphosed stratiform zinc ore bodies.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Zincite information at mindat.org
Significant Gem Localities
USA
 
  • New Jersey
    • Sussex Co.
      • Franklin Mining District
        • Franklin
        • Ogdensburg
          • Sterling Hill
Copyright © Jolyon & Katya Ralph 1993-2019. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.