THE MINERAL PLANCHEITE

  • Chemistry: Cu8Si8O22(OH)4 - H2O, Hydrated Copper Silicate Hydroxide
  • Class: Silicates
  • Subclass: Inosilicates
  • Uses: A very minor ore of copper and as mineral specimens.
  • Specimens

Plancheite is another in the long list of secondary copper minerals.And like so many of them, this one is colorful, attractive, has interesting crystal habits and is definitely a good collection mineral.Its almost turquoise-like color is unique and its typical fibrous, radial habit makes for simply a one-of-a-kind mineral. It is named for J. Planche, who first brought specimens of plancheite from the Congo region to the mineralogical community.Plancheite can be found with other colorful secondary copper minerals such as dioptase, shattuckite, conichalcite, brochantite and chrysocolla,making some specimens a treasure trove of rare minerals.

PHYSICAL CHARACTERISTICS:

  • Color is commonly a pale blue, greenish blue to almost turquoise blue and dark blue in some specimens.
  • Luster is vitreous to silky.
  • Transparency specimens are translucent to opaque.
  • Crystal System is orthorhombic.
  • Growth Habits include spherulites or sprays of acicular or fibrous radial crystal clusters. Other habits include massive, mammillary and fibrous aggregates and tiny tabular or platy crystals.
  • Cleavage is not discernible
  • Fracture is fibrous
  • Hardness is 5.5.
  • Specific Gravity is approximately 3.6 - 3.8 (above average for a non-metallic mineral).
  • Streak is pale blue.
  • Associated Minerals are cerussite, dioptase, limonite, melanotekite, quartz, shattuckite, bindheimite, conichalcite, brochantite, "bisbeeite"; (a variety of chrysocolla), and other chrysocolla varieties, and other secondary copper minerals.
  • Notable Occurrences include the type locality of Mindouli, Congo as well as Tantara and Kambowe, Shaba, of the Democratic Republic of Congo and several copper deposits in Arizona, especially the Table Mountain Mine.
  • Best Field Indicators are color, crystal habit, density, locality and associations.
PLANCHEITE specimens:
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PLANCHEITE specimen pln-1
$ 35.00
Dims: 1.4 x 1.2 x 0.7" (3.6 x 3.0 x 1.8 cm)
Wt: 9.8 g
Mashamba Mine, Shaba Province, Zaire
This beautiful thumbnail piece consists almost entirely of Plancheite. It occurs in the form of tiny, fibrous crystals whose clusters form an undulating, botryoidal crust, which likely lined a hollow in a rock that has since eroded away or been removed. It has the classic pale blue coloration of its species and shows a silky luster. Only a very small amount of what appears to he a limonite host rock is present.
no photo
pln-1 ($ 35.00)
Mashamba Mine, Shaba Province, Zaire
PLANCHEITE specimen pln-2
$ 38.00
Dims: 1.2x0.8x0.4" (3.0x2.1x1.1cm)
Wt: 0.21 oz. (5.9g)
Shangulowe, Zaire
This thumbnail specimen of plancheite consists of dozens of radial sprays of acicular crystals. The crystals (in tiny puffballs) are a perfect turquoise color, and are translucent. Also on this specimen are radial sprays of a bright green mineral, which I suspect is brochantite. The tips of both minerals are frequently accompanied by an acicular white mineral, which I cannot identify, and which obscures the deep colors of the underlying minerals. With a loupe, the brightness and clarity of the plancheite (and brochantite) is apparent.
no photo
pln-2 ($ 38.00)
Shangulowe, Zaire

 


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