Formula: Co3(AsO4)2.8H2O
Hydrated normal arsenate, vivianite group, forms a series with annabergite, cobalt-bearing mineral
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

Hydrothermal 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, roselite-β (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 roselite-β (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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