Heterosite (rare) with Ferrisicklerite (ex David Garske Collection)

Item Description

A cool rarity from the Bull Moose Mine in South Dakota. The piece comes from the collection of mineralogist David H. Garske, and was self-collected. Heterosite is a rare iron phosphate, that resembles Purpurite (they actually form a series), but I've never seen an example from this locality before this specimen. Beautiful purplish Heterosite can be seen on the front edge of the specimen, which is associated with / sitting on brownish-black Ferrisicklerite. Now Heterosite forms as an alteration from preexisting phosphates like Triphyllite or Lithiophilite, and usually an intermediate alteration of species like Ferrisicklerite are commonly seen. These specimens are RARE from South Dakota, so if you collect phosphate, US minerals, or simply rarities, don't miss out on this one.