Editorial Feature

Buckhornite - Occurrence, Properties, and Distribution

Jun 3 2014

Buckhornite is an orthorhombic-dipyramidal black mineral, containing tellurium, sulfur, lead, gold, and bismuth.

It was first described in 1992 from the Buckhorn mine, near Jamestown in Boulder, Colorado, USA. The mineral was named after its locality of discovery.

Properties of Buckhornite

The following are the key properties of Buckhornite:

Cell Data
- Space Group: Pmmm
- a = 4.073–4.092
- b = 12.245–12.326
- c = 9.322–9.374
- Z = 2

Crystal Data
- Orthorhombic
- Point Group: 2/m 2/m 2/m
- Euhedral to subhedral bladed crystals, flattened ⊥ {100}, to 1.5mm, may be foil-like, warped, bowed, or in helical spirals; commonly aggregated in clusters
- X-ray Powder Pattern: 2.763 (vvs), 2.390 (vvs), 3.739 (vs), 3.108 (vs), 2.456 (vs), 2.044 (s), 1.7084 (s)

Chemical Composition

Elements	Content 1	Content 2	Content 3
Pb	34.5	37.02	35.37
Te	22.3	22.38	21.78
Bi	18.4	12.41	17.83
Au	17.0	16.97	16.81
S	7.8	8.17	8.21
Cu	0.1	-	-
Sb	-	3.26	-
Total	100.1	100.21	100.00

Optical Properties
- Optical Class: Biaxial
- Pleochroism: Distinct; purplish-gray to pale blue

Estimated Properties

Electron density	Bulk density (electron density) = 6.73 g/cm³ note: Specific gravity of Buckhornite = 8.25 g/cm³
Photoelectric	PE_Buckhornite = 1379.89 barns/electron U = PE_Buckhornite x ρElectron density = 9288 barns/cm³
Fermion index	Fermion index = 0.09 Boson index = 0.91
Radioactivity	Buckhornite is not radioactive

How to Identify Buckhornite

Buckhornite can be identified by its black color, with metallic luster, and gray streak. Its cleavages are perfect, and its fractures are sectile. The mineral is opaque in nature, and it can be formed as euhedral or thin, lath-like crystals.

The relative hardness of buckhornite is 2.5.

Global Distribution

Buckhornite is distributed in the following places:

Buckhorn Pb–Ag mine, 1.6km north-west of Jamestown, Boulder Co. Colorado, USA
Golden Sunlight mine, near Whitehall, Jefferson Co. Montana
Pepr and Bohuliby mines, J´ilov´e gold deposit, 30km south-east of Prague, Czech Republic
Megradzor district, Armenia

Occurrence of Buckhornite and Useful Mineral Association

Buckhornite occurs in hydrothermal Au–Te-bearing deposits.

The minerals that are closely associated with buckhornite include tetradymite, melonite, pyrite, gold, calaverite, galena, altaite, tellurobismuthite, nagyagite, hematite, sphalerite, chalcocite, bornite, covellite, and aikinite.