Sep 3 2013
Benjaminite was first discovered in 1924 from the Outlaw Mine, 12 miles north of Manhattan, Nye Co. Nevada, USA. The mineral was named after Dr. Marcus Benjamin of the U.S. National Museum.
Properties of Benjaminite
The following are the key properties of Benjaminite:
- Cell Data
- Space Group: C2/m
- a = 13.25(2)
- b = 4.05(1)
- c = 20.25(3)
- β = 103.14(07)°
- Z = 2.
- Crystal Data
- Monoclinic
- Point Group: 2/m
- Massive and as laths, to 6 mm, which are complex inter-growths of several closely related phases. Twinning: Polysynthetic, common
- X-ray Powder Pattern: 2.851 (100), 3.539 (80), 3.427 (80), 2.813 (60), 2.022 (60), 2.007 (60), 3.302 (50).
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
| Bi |
65.1 |
64.8 |
| S |
16.4 |
18 |
| Ag |
12.6 |
14.2 |
| Pb |
3.7 |
0.6 |
| Cu |
1.4 |
- |
| Total |
99.2 |
97.6 |
- Optical Properties
- Estimated Properties
| Electron density |
Bulk density (electron density) = 4.69 g/cm3
note: Specific gravity of Benjaminite = 4.91 g/cm3 |
| Photoelectric |
PEBenjaminite = 21.27 barns/electron
U = PEBenjaminite x ρ Electron density = 99.79 barns/cm3 |
| Fermion index |
Fermion index = 0.01
Boson index = 0.99 |
|
Radioactivity
|
Benjaminite is not radioactive. |
How to Identify Benjaminite
Benjaminite is a copper or grayish yellow mineral having opaque appearance, metallic luster and fair cleavage. It exhibits non-magnetic and non-fluorescent characteristics. The density of the mineral is 6.7 g/cm3, and its hardness is 3.5.
Global Distribution
Benjaminite is distributed in the following places:
- Outlaw mine, about 17 km north of Manhattan, Round Mountain district, Nye Co., Nevada.
- Alaska mine, Poughkeepsie Gulch, near Ouray, San Juan Co., Colorado.
- Terra Company mine, Camsell River, Northwest Territories.
- Canadian Keely mine, Cobalt, Ontario, Canada.
- Porvenir mine, Cerro Bonete, Potosi, Bolivia.
- Pirquitas deposit, Riconada Department, Jujuy Province, Argentina.
- AW mine, south of Tenterfield, New South Wales, Australia.
- Nanten and Daimaru veins, Ikuno deposits, Hyogo Prefecture, Japan.
- Svishti Plaz gold deposit, central Balkan Mountains, Bulgaria.
- Waschgang Au–Cu deposit, Goldberg Mountains, Upper Carinthia, Austria.
Occurrence of Benjaminite and Useful Mineral Association
Benjaminite occurs in a quartz vein near the contact of a soda-granite and an intrusive rhyolite, veinlet in calcite, and molybdenite pipe deposit. It also occurs in arsenides. The mineral is closely associated with bismuthinite, bismuth, molybdenite, silver, galena, sphalerite, pyrite, chalcopyrite, matildite, nickeline, arsenopyrite, arsenopyrite, skutterudite, safflorite, quartz, molybdenite, muscovite and aikinite.
References