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.
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
chrysocolla,making some specimens a treasure trove of rare
- 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,
"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.