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Formula: Co3(AsO4)2.8H2O
Hydrated normal arsenate,
vivianite group, forms a series with
annabergite,
cobalt-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.07
Hardness: 2
Streak: Pink
Colour: Red
Solubility: Insoluble in water, nitric and sulphuric acid; soluble in hydrochloric acid
Common impurities: Ni,Fe,Zn
Environments:
Erythrite is a rare secondary mineral that occurs in the
oxidation zone of some
nickel-cobalt-arsenic
mineral deposits as an alteration product of
cobalt arsenides. It is rarely
present in large amounts and usually forms as crusts or fine aggregates filling cracks. Associated minerals include
cobaltite, skutterudite,
symplesite, anorthoroselite
(triclinic paramorph of roselite),
scorodite, pharmacosiderite,
adamite, morenosite,
retgersite and malachite
(HOM, Dana, Mindat).
At the Desolation prospect, Mount Isa Block, Queensland, Australia, a few sprays of erythrite crystals to 5 mm have
been found in chert associated with
heterogenite and manganese oxides
(AJM 17.2.85).
The type locality is the Daniel Mine, Neustädtel, Schneeberg, Erzgebirgskreis, Saxony, Germany.
At Reichelsdorf, Hessen, Germany, erythrite occcurs with skutterudite
(FM 47628).
Bou Azzer has produced the finest specimens of erythrite in the world, exceptionally up to 6 cm. It is produced by
the alteration of cobalt arsenides and sulphosalts such as
skutterudite.
Common associates are cobaltkoritnigite,
arsenolite and lavendulan,
and sometimes anorthoroselite
(triclinic paramorph of roselite),
picropharmacolite or
annabergite.
Erythrite rests most comonly on quartz,
dolomite and skutterudite, and
sometimes on talmessite
(Minrec 38.5.371-374).
At Roughton Gill mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, UK, erythrite has been reported as
coatings on quartz and calcite
(JRS 14.12).
At Brownley Hill mine, Alston Moor, Eden, Cumbria, UK, erythrite has been found associated with
sphalerite, ankerite
and quartz
(Minrec 31.3.245).
In the Blackbird mining district, Lemhi county, Idaho, USA, coatings of erythrite have been found along seams and
cracks in a black tourmaline-quartz
rock
(Minrec 41.4.362-363).
In the Black Hawk district, Grant county New Mexico, USA, erythrite has been found with
annabergite
(Dana).
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