ZINKENITE
Specimen zik-4

Dims: 2.8 x 2.2 x 1.7" (7.1 x 5.6 x 4.3 cm)

Wt: 8.48 oz. (240.6 g)

Brobdignag Mine, Silverton, Colorado, U.S.A.

This rather simple, small hand specimen consists of an amorphous chunk of Zinkenite, a rather complex lead and antimony sulfide. The material appears to be a piece of a larger chunk, as only a small portion of its surface is not fresly broken. The fresh areas show a dark gray coloration and a bright metallic luster, and are punctuated by thin crusts and veins of white crystalline calcite that extend through parts of the material. There is no host rock present, however.

Dims: 3.4 x 2.0 x 1.4" (8.6 x 5.1 x 3.6 cm)

Wt: 6.22 oz. (176.4 g)

Itos Mine, Oruro Department, Bolivia

A considerable part of the mass of this hand specimen is made up of intersecting sprays of Zinkenite needles. Most of these sprays are damaged due to the fact that they were exposed through breakage, but many intact crystals are present. Some achieve lengths of over 2" (5 cm), and those that are intact show fair to good hexagonal prismatic form, though intergrowth and cramped space have warped most of them. All have the standard dark gray color and dull metallic luster of their species. They are embedded in a host rock that is made up of several other sulfide minerals including pyrite, chalcopyrite, and what appears to be bornite.

Dims: 2.5 x 1.3 x 0.9" (6.4 x 3.3 x 2.3 cm)

Wt: 1.73 oz. (49.3 g)

Itos Mine, Oruro Department, Bolivia

Scores of Zinkenite clusters make up most of the mass of this small hand specimen. These clusters are each made up of anywhere from 2 to 20 hexagonal needle-like Zinkenite crystals, many of which are damaged or broken. They reach lengths of nearly 2" (5 cm) and appear to have good form, though one crystal that I studied had an asymmetrical diamond-shaped cross-section. They have the standard moderately dark gray color and metallic luster of their species, though a few sprays are dusted with a pale substance that is likely another metallic sulfide. There may be crystals of another metallic sulfide mineral such as boulangerite present, as some of the crystals are at least as thin as human hair, if not thinner. The "base" on which they rest is composed of yet more metallic sulfides, including pyrite, chalcopyrite, and possibly a bit of bornite.

Dims: 1.8 x 1.0 x 0.8" (4.6 x 2.5 x 2.0 cm)

Wt: 1.6 oz. (44 g)

Brobdignag Mine, Silverton, Colorado, U.S.A.

This thumbnail specimen consists of several intersecting clusters of compact, fibrous Zinkenite needles. These needles reach lengths of more than 1.5" (3.8 cm) and appear to be in good condition. Their hexagonal form is essentially impossible to define, but a few of the compact "clusters" appear to have natural terminations. Their moderately dark silvery-gray color and metallic luster are standard for their specie. No other material is present. According to the accompanying documentation, the Brobdignag Mine is the first U.S. locality for this specie.

Dims: 1.66x0.78x0.51" (4.21x1.99x1.29cm)

Wt: 0.61oz (17.2g)

San Jose Mine, Orure, Bolivia

This specimen is pure zinkenite, as a tightly intergrown mass of fine silvery needles. These are organized in a half-dozen bundles suggesting that many starting points for the essentially radial growth. The color is silver on one side, slightly golden on another, and the specimen appears significantly darker on the third. Under a loupe, it appears that these are simple tarnishes of the zinkenite, parts of which appear irridescent. Also, the crystals no longer appear as needles, but rather as long prismatic crystals, and many more randomly oriented crystals are apparent. I suspect that the silvery side is the freshly exposed surface, with the tarnish due to varying degrees of oxidation.

Dims: 1.15x0.98x0.75" (2.92x2.48x1.89cm)

Wt: 0.45oz (12.8g)

San Jose Mine, Oruro, Bolivia

Zinkenite is commonly found as very fine acicular fibers, sometimes coating a surface with a fur-like coating, similarly to jamesonite or millerite. But not this specimen. For this specie, these crystals are large, looking like small crystals of stibnite. But a loupe shows that these crystals have a hexagonal cross section, and terminations that appear basal on one end and jagged on the other. Also, some of the crystals are very thin and very long. All have a dark steel-gray color and metallic luster. The loupe also reveals that there is a fine coating of very tiny zinckenite crystals on the larger crystals on one side of the specimen - they both dull and darken the appearance.