Collinsit crystals from the Tip Top Mine, South Dakota, USA, Gerd Tremmel collection – 2 miniature specimen as unique piece
These two miniature specimens show Collinsite crystals from the Tip Top Mine, South Dakota, USA, from the Gerd Tremmel collection. The dark brown to gray brown matrix displays irregular fracture surfaces with a rough and compact structure. In small cavities and on the surface, light gray to whitish Collinsite crystals occur as fine crystalline aggregates. The crystals partially emerge from the host rock and form subtle contrasting zones within the massive matrix. The interplay between the dark host rock and the lighter crystal areas gives the specimens a clearly structured and natural appearance.
Geology & Origin
The Tip Top Mine in South Dakota is part of a pegmatitic system within the Black Hills region, which is well known for its diversity of phosphate minerals. Collinsite forms here as a secondary calcium magnesium phosphate in the weathering and alteration zone of primary phosphate rich minerals. Its formation took place under oxidizing conditions through the circulation of mineral rich solutions in fractures and cavities of the pegmatite. Such secondary phosphates are characteristic of the complex geochemical evolution of this classic American locality.