Cyanotrichite is a 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...

 aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 sulfate

Sulfate

In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...

 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...

, 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...

₄Al₂[(O

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...

H

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

)₁₂|S

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

O₄]·2H₂O

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, also known as lettsomite, very similar to halotrichite

Halotrichite

Halotrichite, also known as feather alum, is a highly hydrated sulfate of aluminium and iron. It is formed by the weathering and decomposition of pyrite commonly near or in volcanic vents. Its chemical formula is FeAl24·22H2O. It forms fibrous monoclinic crystals. The crystals are water...

, and a member of the same group. However, it is much rarer. It forms velvety aggregates of extremely fine fibres and radial aggregates. It crystallizes in the orthorhombic system and forms translucent bright blue acicular crystal clusters or drusey coatings. The Mohs hardness is 2 and the specific gravity

Specific gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 ranges from 2.74 to 2.95. Refractive indices

Refractive index

In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

 are nα=1.588 nβ=1.617 nγ=1.655. It is an oxidation product of primary copper mineralization in a weathering environment with abundant aluminium and sulfate. Associated minerals include brochantite

Brochantite

Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M...

, spangolite, chalcophyllite

Chalcophyllite

Chalcophyllite is a rare secondary copper arsenate mineral occurring in the oxidized zones of some arsenic-bearing copper deposits. It was first described from material collected in Germany...

, olivenite

Olivenite

Olivenite is a copper arsenate mineral, formula Cu2AsO4OH. It crystallizes in the monoclinic system , and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces...

, tyrolite

Tyrolite

Tyrolite is a hydrated calcium copper arsenate carbonate mineral with formula: CaCu52CO34·6H2O. Tyrolite forms glassy blue to green orthorhombic radial crystals and botryoidal masses. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.1 to 3.2...

, parnauite, azurite

Azurite

Azurite is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France...

 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...

.

The main deposits are Cap la Garrone in the Var

Var (département)

The Var is a French department in the region Provence-Alpes-Côte d'Azur in Provence, in southeast France. It takes its name from the river Var, which used to flow along its eastern boundary, but the boundary was moved in 1860...

 (France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

), Romania

Romania

Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

 and Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

 (USA). Because of its beautiful colouring, it is very popular with collectors.

It was first described in 1839 from Moldova Nouă

Moldova Noua

Moldova Nouă is a town in southwestern Romania in Caraş-Severin County , in an area known as Clisura Dunării. It is located on the shores of the river Danube. In 2002, Moldova Nouă had a population of 13,917...

, Banat, Romania. The name is from Greek kyaneos for "blue" and triches for "hair" referring to the typical color and habit.