Zincite

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Insert non-formatted text here Danburite

Zincite

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Zincite

Chemical composition

(Zn,Mn)0

Zinc manganese oxide

Crystal system

hexagonal

Habit

Pyramidal (hemihedral); massive

Cleavage

Perfect on {10-10}; Parting on {0001}

Fracture

conchoidal

Hardness

4

Optic nature

Uniaxial +

Refractive index

2.013 – 2.029

Birefringence

 

Dispersion

 

Specific gravity

5.66

Lustre

Sunadamantine to resinous

Pleochroism

 

Fluorescence

Pale yellow (Extremely rare!)

Contents

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Crystal System:  hexagonal

Crystal Habit: crystals pyramidal and distinctly hemimorphic; massive

Composition: zinc oxide, ZnO. Usually with minor amounts of manganese (less than 7%), and minor to trace amounts of iron, magnesium and aluminum.

Diagnostics:

        Because of its high specific gravity, zincite is unlikely to be confused with any other gem material.

Color: Deep red, deep orange. Manganese is the coloring agent. Green zincite has been observed in nature but to date has not been found in sizes sufficient to facet.

Magnification: black submetallic inclusions of franklinite or hetaerolite (both oxides containing zinc and manganese) are common

Optical and Physical Properties:

Cleavage: perfect on {10-10} ; parting on {000-1}
Fracture: conchoidal
Specific Gravity
:  5.66 (measured) 5.67 (calculated)
Hardness: 4
Lustre:  subadamantine to resinous
Optical Nature
:  uniaxial (+)
Refractive Index: ε = 2.013  ω = 2.029
Birefringence:   
Dispersion:
Pleochroism:
Spectroscope:

Treatments: none known

Phenomenon: zincite may, in extremely rarely instances, display a pale yellow fluorescence in long wave ultraviolet light. This has not yet been documented in cut stones.

Synthetics:

Synthetic zincite flooded the US market in the late 1980’s and 1990’s,  available in a rainbow of colors from pale green to green, pale red to deep red, and yellow to deep orange synthetic. This material was derived from the smokestacks of a metal refinery in Silesia, Poland, where it had crystallized over many years from volatized zinc oxide. Zincite is also grown in laboratories by several techniques, including hydrothermal, Czochralski pull, and vapor deposition (sublimation)  methods.

Imitations: none reported

Occurence: the zinc mines of Franklin and Ogdensburg in Sussex County, New Jersey.

Sources:

Anthony, John W., Bideaux, Richard A., Bladh, Kenneth W., and Nichols, Monte C. (1990): Handbook of Mineralogy: Mineral Data Publishing, Tucson, Arizona,

Dunn, Pete J. (1995) Franklin and Sterling Hill, New Jersey: the world’s most magnificent mineral deposits

Palache, C. (1935), Minerals of Franklin and Sterling Hill, New Jersey, USG Professional Paper 180

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Seventh edition

External Links: