THE MINERAL CONICHALCITE

Chemistry: CaCuAsO4(OH), Calcium Copper Arsenate Hydroxide
Class: Phosphates
Subclass: Arsenates
Group: Adelite
Uses: A minor ore of copper and as mineral specimens.
Specimens

Conichalcite has a sparkling grass green color that once observed is hard to mistake for any other mineral. It is often encrusted onto limonitic rocks that have a red to yellow color and the two produce a very colorful specimen. Conichalcite forms in the oxidation zone of copper ore bodies. Oxygen rich ground water that might react with copper sulfide and/or copper oxide minerals produce a wonderful assortment of attractive and colorful minerals in a zone called the oxidation zone. Conichalcite is just one of these minerals. Other oxidation zone minerals include malachite, azurite, linnarite, etc.

Conichalcite forms a solid solution series with the mineral calciovolborthite. A solid solution series occurs when two or more structurally identical minerals can interchange elements within their chemistries without dramatically altering the crystal structure. In the case of conichalcite and calciovolborthite the two elements are arsenic and vanadium. Conichalcite is the arsenic rich end member of the series and calciovolborthite is the vanadium rich end member.

PHYSICAL CHARACTERISTICS:

Color is grass green to light green.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System is orthorhombic
Crystal Habits include the crusts of acicular to almost fibrous crystals. Also as botryoidal masses and compact crusts.
Cleavage is absent.
Fracture is uneven.
Hardness is 4.5
Specific Gravity is approximately 4.3 (heavy)
Streak is green.
Associated Minerals are limonite, malachite, beudantite, adamite, cuproadamite, olivenite and smithsonite.
Notable Occurrences include Juab Co., Utah, Nevada and Arizona, USA; Mexico; Chile; Poland and Zaire.
Best Field Indicators are crystal habit, color, associations and density.