THE MINERAL CUBANITE

  • Chemistry: CuFe2S3, Copper Iron Sulfide.
  • Class: Sulfides
  • Uses: A very minor ore of copper and as mineral specimens.
  • Specimens
Cubanite (also known as "chalmersite") is a rare copper mineral that does not contribute much to the supply of copper. It would not even be considered an ore of copper except that it is often interbedded with other ores of copper and so it does contribute some copper when these other ores, such as chalcopyrite, are processed. Cubanite is also associated with gold in some gold mines.

It is far more desired as a mineral specimen. Cubanite has a bright metallic luster and a brassy golden color that is really striking. It commonly forms twins that are seen as either sharply pointed chevrons or as cyclic twins of six rayed "stars" or "flowers". Cubanite is named after Cuba, the country of its type locality.

PHYSICAL CHARACTERISTICS:

  • Color is a brassy golden yellow.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include elongated prismatic to tabular crystals. Crystals sometimes twinned into chevrons and six rayed cyclic "stars" or "flowers". Also lamellar, rarely massive.
  • Cleavage is rather poor in one direction.
  • Fracture is conchoidal.
  • Hardness is 3.5 - 4
  • Specific Gravity is approximately 4.1 (average for metallic minerals)
  • Streak is black.
  • Other Characteristics: Deep longitudinal striations on most crystal faces.
  • Associated Minerals are chalcopyrite, quartz, gold, siderite, calcite, pyrite, pyrrhotite and several copper sulfides.
  • Notable Occurrences include Barracanao, Cuba; Morro Velho gold mine, Minas Gerais, Brazil; Harz Mnts, Germany and the Henderson Mine, Chibougamau, Quebec, Canada.
  • Best Field Indicators are crystal habit especially its twins, color, luster and occurrence.
CUBANITE specimens:
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CUBANITE specimen cub-1
$ 150.00
Dims: 4.0" x 1.4" x 1.3" (10.2 x 3.6 x 3.3 cm)
Wt: 4.24 oz. (120.4 g)
Henderson Mine #2, Chibougamau, Quebec, Canada
A crust made up of small Cubanite crystals partially coats the limestone host rock of this specimen. Most of the crystals are extremely small, not exceeding 1 or 2 mm in diameter, but one approaches 1/4" (7-8 mm), and there is part of a single face visible that spans almost 0.5" (1.3 cm). There is only a small amount of visible damage on the crust. The crystals are prismatic and appear to be hexagonal, which means that the Cubanite has undergone cyclic twinning. A few of the crystals, however, appear not to have a symmetrical shape, but this may be due to growth-related abnormalities. They have a dull golden color that appears more orange or brown in some areas and a metallic luster. They rest among a bed of small, colorless, transparent blades of calcite that also partially coat the black limestone host rock.
no photo
cub-1 ($150.00)
Henderson Mine #2, Chibougamau, Quebec, Canada
CUBANITE specimen cub-2
$ 60.00
Dims: 1.6 x 1.3 x 1.2" (4.1 x 3.3 x 3.1 cm)
Wt: 2.0 oz. (58 g)
Marathon, Ontario, Canada
This hand specimen consists of a black and white host rock in which are embedded a few chunks of Cubanite. As only broken surfaces of the mineral are exposed, it is impossible to assess its crystal form, if it has any. It does have the standard brassy yellow color and metallic luster of its specie, and is accompanied by either some chalcopyrite or bornite, with its colorful iridescence.
no photo
cub-2 ($ 60.00)
Marathon, Ontario, Canada
CUBANITE specimen cub-3
$ 65.00
Dims: 0.55x0.31x0.28" (1.4x0.8x0.7cm)
Wt: 6.80ct (1.36g)
Henderson #2 Mine, Chibougamu, Quebec, Canada
This is an excellent thumbnail specimen of cubanite. The crystals have a six-sided shape, the faces are striated, and the normal brassy color and metalic luster are evident. Other than the broken faces where the specimen was removed from its host, there is no damage.
no photo
cub-3 ($ 65.00)
Henderson #2 Mine, Chibougamu, Quebec, Canada
CUBANITE specimen cub-4
$ 55.00
Dims: 0.55x0.38x0.29" (1.40x0.97x0.73cm)
Wt: 5.8ct (1.16g)
Henderson #2 Mine, Chibougamu, Quebec, Canada
This is a cluster of cubanite crystals, the largest of which (over 7mm wide and 6mm long) dominates the specimen. While some smaller crystals are complete, the termination of the largest one is rather complex, largely due to the intergrowth of other cubanite crystals. The cubanite crystals have fine striations along their sides, and a brassy color with a metallic luster.
no photo
cub-4 ($ 55.00)
Henderson #2 Mine, Chibougamu, Quebec, Canada
 

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