Denningite , Tellurite Locality: Moctezuma Mine (Bambolla Mine), Moctezuma , Municipio de Moctezuma , Sonora , Mexico ( Locality at mindat.org ) Size: 5.5 x 4.3 x 2.2 cm. Denningite is found only at this mine, the type locality for the species recognized in 1961 from material found in the 1940s-1950s. One of the surprises of 2007 for rarities was the reworking of the famous old Bambolla mine in the Moctezuma tellurium complex for specimens, by several European-led collecting teams. Many specimens were then sold at Munich 2008 and this year in Tucson. This is a very rich specimen with vitreous, very nice yellow, elongated crystals of denningite admixed with microcrystalline or acrystalline yellow tellurite. I am told that mixed with the denningite is often spiroffite, and the two are often mislabeled one way or the other, but this has not been determined for this specimen. Type locality. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Denningite
Denningite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaMn²⁺Te⁴⁺₄O₁₀.
It crystallizes in the tetragonal crystal system (space group P4_2/nbc).
Key properties: Mohs hardness 4; specific gravity 5.05; White streak; Adamantine luster; optically uniaxial.
IMA symbol Dnn, IMA status: approved, named in 1963.
Found in a hydrothermal Au–Te deposit.
It is found associated with Tellurium, tellurite, paratellurite, spiroffite, zemannite.
The mineral was named to honor Reynolds McConnell Denning (1916–1967), Professor of Mineralogy, University of Michigan, Ann Arbor, Michigan, USA.