Novákite Locality: Černý Důl (Schwarzenthal), Krkonoše Mtn (Riesengebirge), Hradec Králové Region, Bohemia (Böhmen; Boehmen), Czech Republic Dimensions: 3 cm x 1.7 cm x 1.5 cm Novakite is a very rare copper, silver arsenide found in only three localities worldwide and was discovered in 1959. This specimen, dating to 1961, is from the Type Locality in Bohemia. Pods and stringers of matte, metallic-gray, massive novakite are scattered on all sides of the quartz matrix. The largest pod is 8 mm across. Ex. Josef Vajdak Collection, a noted Czech specialist. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Novákite
Novákite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula (Cu,Ag)₂₁As₁₀.
It crystallizes in the tetragonal crystal system (space group C2/m).
Key properties: Mohs hardness 3–3.5; specific gravity 8.01; Black streak; Metallic. Anisotropism: Medium, dark blue-gray and pale brown-ocher. R1 –R2: (400) 43.6–49.0, (420) 45.4–50.5 luster.
IMA symbol Nvá, IMA status: approved, named in 1959.
Found in hydrothermal carbonate veins up to 20 cm thick, cutting diopside hornfels lenses in pyroxene gneiss and less commonly in mica schist (Černý Důl mine, Czech Republic).
It is found associated with Arsenic, arsenolamprite, koutekite, silver, löllingite, chalcocite, skutterudite, chalcopyrite, bornite, uraninite, calcite (Černý Důl mine, Czech Republic).
In honor of Jiřı́ Novák (1902–1971), Professor of Mineralogy, Charles University, Prague, Czech Republic.