mineral

Erythrite on Matrix

Cobalt Bloom (Co3(AsO4)2·8H2O)

Hardness: 1.5-2.5; Color: Crimson, peach-red, or violet-purple; Luster: Pearly to adamantine; Crystal system: Monoclinic; Cleavage: Perfect; Specific gravity: 3.06

Hardness: 1
Color: Crimson, peach-red, or violet-purple
Luster: Pearly to adamantine

Identified July 20, 2026More mineral →

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Physical properties

Hardness: 1.5-2.5; Color: Crimson, peach-red, or violet-purple; Luster: Pearly to adamantine; Crystal system: Monoclinic; Cleavage: Perfect; Specific gravity: 3.06

Formation & geological history

Secondary mineral formed through the oxidation of cobalt-bearing arsenic minerals like cobaltite or skutterudite in hydrothermally altered veins.

Uses & applications

Used primarily as a geological indicator ('ore guide') in the search for native silver and cobalt deposits; also highly prized by mineral collectors for its vibrant color.

Geological facts

Known as 'Cobalt Bloom' because its vibrant pink-purple color stands out against dark rock. It was historically used to locate cobalt and silver ores. It is chemically related to annabergite (Nickel Bloom).

Field identification & locations

Identified by its distinctive magenta/purple color and micaceous cleavage. Often found with silver, nickel, or cobalt ores in locations like Morocco, Canada (Cobalt, Ontario), and Germany.