Olivenite

Locality: Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany Photo Copyright © Chinellato Matteo

Chemical Formula: Cu2(AsO4)(OH)
Locality: Carharrack mine, Gwennap, Cornwall, England, GB
Name Origin: From the German olivernerz, literally “olive” ore, in allusion to its typical color.

Olivenite is a copper arsenate mineral, formula Cu2(AsO4)(OH). It crystallizes in the monoclinic system (pseudo-orthorhombic), and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. More commonly, it occurs as globular aggregates of acicular crystals, these fibrous forms often having a velvety lustre; sometimes it is lamellar in structure, or soft and earthy.

A characteristic feature, and one to which the name alludes (German, Olivenerz, of A. G. Werner, 1789), is the olive-green color, which varies in shade from blackish-green in the crystals to almost white in the finely fibrous variety known as woodcopper. The hardness is 3, and the specific gravity is 4.3. The mineral was formerly found in some abundance, associated with limonite and quartz, in the upper workings in the copper mines of the St Day district in Cornwall; also near Redruth, and in the Tintic Mining District in Utah. It is a mineral of secondary origin, a result of the oxidation of copper ores and arsenopyrite.

The arsenic of olivenite is sometimes partly replaced by a small amount of phosphorus, and in the species libethenite we have the corresponding copper phosphate Cu2PO4OH. This is found as small dark green crystals resembling olivenite at Libethen in the Slovak Republic, and in small amount also in Cornwall. Other members of this isomorphous group of minerals are adamite, Zn2(AsO4)(OH), and eveite, Mn2(AsO4)(OH).

History

Discovery date : 1820
Town of Origin: CORNOUAILLES
Country of Origin: ANGLETERRE

Physical Properties

Hardness: 3,00
Density: from 4,37 to 4,38
Color : olive-green; greenish brown; yellow; grayish green; yellowish white; blackish green; brown; grayish white
Luster: vitreous;silky; greasy
Streak : green yellow; white
Break: irregular; conchoidal
Cleavage: {110} Indistinct, {010} Indistinct, {110} Indistinct

Photos:

OLIVENITE Wheal Phoenix, Linkinhorne, Liskeard, Cornwall, England, Europe Size: 6.5 x 6 x 3 cm (Small Cabinet) Owner: Crystal Classics
Olivenite Inubia mine, Bahia, Brazil Specimen weight:76 gr. Crystal size:3 mm Overall size: 72mm x 60 mm x 30 mm minservice
Olivenite Mine du Cap Garonne, Pradet, Var, Provence-Alpes-Côte d’Azur, France Specimen weight:18 gr. Crystal size:0,15 cm Overall size:4 x 3,7 x 1,3 cm minservice
OLIVENITE on CORNWALLITE Wheal Phoenix, Linkinhorne, Liskeard, Cornwall, England, Europe Size: 5 x 3 x 2.5 cm (Small Cabinet) Owner: Crystal Classics
SHARE