Erythrite, also known as Red Cobalt or Cobalt Bloom, is a secondary hydrated cobalt arsenate mineral that crystallizes in the form of crusts, aggregates and tiny needle-like prismatic crystals. It's a member of the Vivianite family and usually occurs around other Cobalt varieties. It can also be associated with natural Silver. The color is mainly crimson red, but can also be seen as purple, pink, peach, and grey. Lighter color Erythrite usually indicates higher levels of Nickel.
Erythrite crystallizes in the monoclinic system and forms prismatic crystals. The color is crimson to pink and occurs as a secondary coating known as cobalt bloom on cobalt arsenide minerals. They also have multiple forms; Erythrite crystals can be radial or stellate aggregates, drusy or fibrous. Common Erythrite is powdery and massive, while striated, prismatic crystals are quite rare.
