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Formula: Cu2(AsO4)(OH)
Anhydrous arsenate containing hydroxyl, olivenite group, forms a series with
libethenite and with
adamite.
Crystal System: Monoclinic
Specific gravity: 4.46 measured, 4.45 calculated
Hardness: 3
Streak: Olive-green to brown
Colour: Olive green to yellow or brown, grey-green, greyish white; light green in transmitted light.
Solubility: Soluble in acids and in ammonia
Common impurities: Fe,P
Environments:
Olivenite is a relatively common, thermodynamically very stable,
secondary
copper
mineral found in the oxidised zones
of copper deposits containing arsenic-bearing phases, especially
tennantite and enargite
(Mindat). It is the most common secondary copper arsenate in
the oxdised zone of hydrothermal copper
deposits.
Associated minerals include clinoclase,
conichalcite,
tyrolite, cornetite,
cornwallite,
metazeunerite, scorodite,
pharmacosiderite,
spangolite, chalcophyllite,
brochantite, malachite,
azurite and chrysocolla
(HOM).
Localities
At the Block 14 open cut, Broken Hill, New South Wales, Australia, olivenite occurs with
beudantite-segnitite,
bayldonite, mawbyite and
mimetite. Later sulphate minerals such as
brochantite and linarite
also occur on some specimens
(AJM 3.1.54).
At the New Cobar deposit, New South Wales, Australia, olivenite occurs in vugs in
quartz,
associated with chenevixite and agardite,
and almost always associated
with partially oxidised arsenopyrite
(AJM 11.2.80).
At the Desolation prospect, Mount Isa Block, Queensland, Australia, olivenite is found on
chrysocolla, associated with clinoclase.
Olivenite and libethenite also occur on earlier
chrysocolla and As-rich
pseudomalachite crusts
(AJM 17.2.86).
At the Bali Lo prospect, Ashburton Downs, Western Australia, olivenite occurs intergrown with
chenevixite
(AJM 13.1.34-35).
At the Telfer gold mine, Western Australia, olivenite has been found radiating from cavity surfaces in
quartz veins overgrown by
chrysocolla
(AJM 12.1.39).
At the Clara mine, Near Wolfach in the Black Forest, Germany, olivenite and its associated minerals
agardite-(Ce), cornwallite and
clinoclase, are perched on a
fluorite
and/or baryte matrix with disseminated
tetrahedrite-tennantite. Also an
olivenite-adamite solid solution is found associated with
philipsburgite
(R&M 90.1.45).
At Ightem, Bou Azzer, Morocco, zinc-rich olivenite occurs associated with
powellite
(MinRec 38.5.385).
At Tamdrost-West, Bou Azzer, Morocco, cobalt and nickel-rich
olivenite has been found in cavities in
quartz
associated with pharmacosiderite
(MinRec 38.5.385).
At Tsumeb, Namibia, olivenite occurs with azurite and
malachite (R&M 93.6.546), and also with adamite,
zincolivenite,
duftite/conichalcite and
arsentsumebite, often on quartz
(R&M 95.3.210-232).
The type localityis the Carharrack Mine, Gwennap, Cornwall, England, UK.
Olivenite from the Carharrack Mine -
Image
At Caldbeck Fells, Cumbria, England, UK, olivenite is rare. At Carrock mine and at Ingray Gill it occurs in cavities in
quartz. At Dry Gill mine it has been found with
beudantite,
and at Old Potts mine it has been found with cornwallite and
conichalcite
(C&S).
At the San Rafael mine, Nye county, Nevada, USA, olivenite occurs within zones containing
mixite and conichalcite in the
rosasite stope. Olivenite has also been documented here in
association with cornubite and
cornwallite
(R&M 85.6.520).
At the Majuba mine, Pershing county, Nevada, USA, olivenite is associated with
cornetite
(Dana).
At the Tintic district, Utah, USA, olivenite is usually the first oxysalt to form during the oxidation of
enargite. It is probably the most common of the
arsenates. Enargite traversed by
a network of olivenite veins is often seen. In colour, olivenite is olive-brown, olive-green,
yellowish green, pure brown or rarely reddish brown. It occurs in every one of the copper mines at Tintic. At the
Centennial Eureka mine, vugs completely lined with crystals of olivenite, up to 2 cm or more, are not uncommon
(MinRec 55.2.215-216).
At the Mammoth mines, olivenite is associated with
clinoclase, tyrolite and
conichalcite
(Dana).
Olivenite from Tintic - Image
Alteration
euchroite (s) to olivenite (s) and H2O (l)
Cu2AsO4(OH). 3H2O ⇌ Cu2AsO4(OH) + 3H2O
(MM 52.684)
The Activity-pH diagram below was calculated at 298.2 K for the main
Cu2+ and Pb2+ arsenate minerals.
Boundaries are calculated for constant activities (roughly equivalent to concentrations) of Pb2+ and Cl-
ions in solution, over a range of values of pH and of Cu2+ activity. Higher chloride activites make the stability
fields of bayldonite and duftite vanish,
with respect to the encroachment of that of mimetite
(LMW p269).
The arsenate mineral formulae are:
philipsbornite PbAl3(AsO4)(AsO3OH)(OH)6
mimetite Pb5(AsO4)3Cl
duftite PbCu(AsO4)(OH)
bayldonite Cu3PbO(AsO3OH)2(OH)2
olivenite Cu2(AsO4)(OH)
cornwallite Cu5(AsO4)2(OH)4
clinoclase Cu3(AsO4)(OH)3
The Activity-pH diagram below was calculated at 298.2 K for some carbonates and
copper arsenates for constant activity (roughly
equivalent to concentration) of H2AsO4- in solution, over a range of values of pH and of
H2CO3 activity
(MM 52.687).
The mineral formulae are:
azurite: Cu3(CO3)2(OH)2
malachite: Cu2(CO3)(OH)2
olivenite: Cu2(AsO4)(OH)
cornubite: Cu5(AsO4)2(OH)4
clinoclase: Cu3(AsO4)(OH)3
The Activity-pH diagram below was calculated at 298.2 K for some arsenates
and sulphates for constant activity (roughly equivalent to concentration) of H2AsO4- in solution,
over a range of values of pH and of SO42- activity
(MM 52.689).
The mineral formulae are:
chalcanthite: Cu(SO4).5H2O
antlerite: Cu2+3(SO4)(OH)4
brochantite: Cu4(SO4)(OH)6
olivenite: Cu2(AsO4)(OH)
cornubite: Cu5(AsO4)2(OH)4
clinoclase: Cu3(AsO4)(OH)3
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