Plancheite is a hydrated copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 silicate

Silicate

A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...

 mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 with the formula Cu

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

₈Si

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

₈O

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

₂₂(OH

Hydroxide

Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...

)₄•(H₂O). It is closely related to shattuckite

Shattuckite

Shattuckite is a copper silicate hydroxide mineral with formula Cu542. It crystallizes in the orthorhombic – dipyramidal crystal system and usually occurs in a granular massive form and also as fibrous acicular crystals. It is closely allied to plancheite in structure and appearance.Shattuckite is...

 in structure and appearance, and the two minerals are often confused.

Structure

Plancheite is a chain silicate

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...

 (inosilicate), with double chains of silica tetrahedra parallel to the c crystal axis. It occurs as sprays of acicular or fibrous radial clusters, with fibers extended parallel to the chains, ie along the c crystal axis; it can also form tiny tabular or platy crystals. It is a member of the orthorhombic crystal class

Orthorhombic crystal system

In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...

 m m m (2/m 2/m 2/m), which is the most symmetrical class in the orthorhombic system.

Properties

Usually a pale turquoise-blue, with a pale blue streak and an adamantine to silky luster

Lustre (mineralogy)

Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....

. It is quite hard, with hardness 5.5 to 6, close to that of feldspar, and specific gravity 3.6 to 3.8. Optically it is biaxial (+)

Birefringence

Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...

, with refractive indices between 1.64 and 1.74, and pleochroic.

Environment

Plancheite is a secondary mineral formed in the oxidized zone of copper deposits, associated with other copper minerals chrysocolla

Chrysocolla

Chrysocolla is a hydrated copper silicate mineral with formula 2H2Si2O54·nH2O.-Properties:Chrysocolla has a blue-green color and is a minor ore of copper, having a hardness of 2.5 to 3.5.-Name and discovery:...

, dioptase

Dioptase

Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine. Its formula is CuSiO3·H2O . It has a hardness of 5, the same as tooth enamel. Its specific gravity is 3.28–3.35, and it has two perfect and...

, malachite

Malachite

Malachite is a copper carbonate mineral, with the formula Cu2CO32. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms...

, conichalcite

Conichalcite

Conichalcite, CaCu, is a relatively common arsenate mineral related to duftite . It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudantite, adamite, cuproadamite, olivenite and smithsonite.- Formation :Conichalcite forms...

 and tenorite

Tenorite

Tenorite is a copper oxide mineral with the simple formula CuO.-Occurrence:Tenorite occurs in the weathered or oxidized zone associated with deeper primary copper sulfide orebodies. Tenorite commonly occurs with chrysocolla and the copper carbonates, azurite and malachite. The dull grey-black color...

. It occurs with primary malachite at the Milpillas Mine in Mexico. The type locality is the Sanda Mine, Mindouli, Pool Region, Republic of Congo.