Mineral sprays
The fine purplish crystals displayed in the photo the rare sulphate mineral Creedite. Several colours are found other than the most common varied yellows, including brown, white, colourless and varied depths of violet. The radiating firework like flower of fine prisms is very characteristic of the mineral’s usual habit, though sprays and crusts also form. It was first named in 1916 after its type locality, Creed Quadrangle in the aptly named Mineral County, Colorado.
Like many of the prettier minerals it is often found as a secondary one, formed by alteration when primary fluorite gets permeated with oxygenated waters during their journey through the rock cycle, usually as erosion is exhuming them close to the surface. Other sources form in low grade (lightly) metamorphosed rocks and skarns, those odd mineral assemblages that form when limestones are baked and stewed in the juices of intruding granites.
It is too soft for jewellery use (4 or so on Mohs scale). Other localities outside the north American West include Mexico, China, Bolivia and the Pamir mountains, shared between Tajikistan and Kazakhstan. This large piece (9.2×5.7×5.2x cm) hails from Mexico and is a pretty top specimen, with many large (for the species) crystal and an unusually intense colour.
Loz
Image credit: Didier Desouens
http://www.mindat.org/min-1151.html
http://www.galleries.com/Creedite
http://bit.ly/28YlDw3
http://bit.ly/28OnHGq
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