Picture width 0.6 mm. Collection and photograph Christian Rewitzer. From: Santo Domingo mine, Caleta Vítor mining district, Arica Province, Arica y Parinacota, Chile. — Photo: Christian Rewitzer · CC BY-SA 3.0
Tondiite
Tondiite is an IMA-recognized mineral species in the halide class, with the chemical formula Cu₃MgCl₂(OH)₆.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Atacamite structural group.
Key properties: Mohs hardness 3–3.5; specific gravity 3.503; Vitreous luster; optically uniaxial.
IMA symbol Ton, IMA status: approved, named in 2013.
Found as a secondary mineral in vesicles in phonolitic tephrite (Vesuvius); a secondary oxidation product of chalcocite, bornite and chalcopyrite in an environment rich in Cl in andesitic porphyric lavas and lava tuff (Chile).
It is found associated with Leucite, sodalite, nepheline, sanidine, Fe oxides and hydroxides (Vesuvius); haydeeite, anhydrite, atacamite (Chile).
The mineral was named to honor Matteo Tondi (1762-1835), an Italian mineralogist and co-author with R.J. Haüy of the classic Traité de Minéralogie.