Nantokite Locality: Carmen Bajo Mine, Nantoko, Copiapó Province , Atacama Region , Chile ( Locality at mindat.org ) Size: 5.2 x 4.3 x 2.3 cm. A very rare example of nantokite, Copper Chloride pure and simple : CuCl. This is according to MINDAT a rare anhydrous copper chloride, known only from arid environments in its natural form. The description goes on to say that it is "Colourless and transparent when fresh. Unstable in humid air, and transforms slowly into greenish secondary Cu-hydroxchlorides" which overlay the natokite now, on its surface. However the crystal cores should remain nantokite, and there should also be material inside this rather large study specimen. From the type locality. Ex. Philadelphia Academy of Sciences Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Nantokite
Nantokite is an IMA-recognized mineral species in the halide class, with the chemical formula CuCl.
It crystallizes in the cubic crystal system (space group F-43m). It is a member of the Sphalerite structural group.
Key properties: Mohs hardness 2.5; specific gravity 3.93–4.3; White streak; Adamantine luster.
IMA symbol Ntk, grandfathered status — known before the IMA’s founding, named in 1867.
Found as a secondary mineral in hydrothermal copper-bearing deposits; rarely in volcanic sublimates.
It is found associated with Cuprite, copper, atacamite, paratacamite, claringbullite, cerussite, hematite.
The name refers to its occurrence near Nantoko, Chile.