Theisite , Azurite Locality: Johann adit, Geyer - Silberberg District, Brixlegg - Rattenberg, Brixlegg - Schwaz area, Inn valley, North Tyrol , Tyrol , Austria ( Locality at mindat.org ) Size: 3.2 x 2.2 x 1.8 cm. A very rare old classic of this copper/zinc arsenate, from an old location that is probably where it was first found, but not first recognized as a new species from. The theisite is the chatoyant, deep green material you can see around the rim of the pocket, lined with a secondary growth of the same or perhaps of malachite, and on which small azurite blades perch. This piece is probably 120-160 years old. Ex. Eric Asselborn Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Theisite
Theisite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₅Zn₅(AsO₄)₂(OH)₁₄.
It crystallizes in the hexagonal crystal system.
Key properties: Mohs hardness 1.5; specific gravity 4.3; White streak; Pearly on cleavages luster; optically biaxial.
IMA symbol Ths, IMA status: approved, named in 1980.
Found as a rare secondary mineral in thin seams cutting other oxidized minerals (near Durango, Colorado, USA); in dolomitized marble (Forno, Italy).
It is found associated with Cuprite, malachite, azurite, kolwezite, partzite, parnauite, anglesite, cerussite, tenorite, adamite, hemimorphite, chrysocolla, zeunerite.
The mineral was named to honor Dr. Nicholas J. Theis, who provided the first specimens.