DIOPTASE WITH MIMETITE & DUFTITE

This large specimen comes out of one of the world's most renowned dioptase producing locales, the Mindouli Region, from the now closed N'tola Mine. There are at least five distinct minerals on this one piece: dioptase, mimetite, duftite, calcite, and dolomite. There appears to be some wulfenite crystals in the assemblage, though we never got the piece analyzed. The mimetite is crystallized in hexagonal bipyramids and dotted along both sides; mimetite and dioptase rarely grow alongside one another. One side shows a large group of small dioptase and mimetite crystals interspersed above patches of botryoidal duftite, complete with a unique bridged arch of dioptase. On the other side, larger dioptase crystals contrast gorgeously against a backdrop of light dolomite. The dioptase ranges in color from the typical emerald green to a bright turquoise color. Throughout the piece one can see cavities in the rock with crystals growing inside and the whole specimen is like its own world. One can easily get lost for hours looking at this specimen through a loupe!

More info:

The N'tola Mine in the Republic of Congo presents a complex dioptase-mimetite paragenesis within dolomitic host rocks through multiple stages of hydrothermal activity. The mineralization sequence began with dioptase formation under oxidizing conditions through copper mobilization from primary sulfides, followed by mimetite precipitation indicating subsequent arsenic and lead enrichment in the mineralizing fluids. This evolving fluid chemistry within the oxidation zone has produced specimens displaying exceptional crystal development, characterized by emerald-green rhombohedral dioptase alongside yellow to brown hexagonal prismatic and bipyramidal mimetite.