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
Tellurite
The orthorhombic mineral form of tellurium dioxide — yellow 'tellurium ocher'.
Intro adapted from Wikipedia (CC BY-SA).
Tellurite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula TeO₂.
It crystallizes in the orthorhombic crystal system (space group Pcab).
Key properties: Mohs hardness 2; specific gravity 5.9; Subadamantine luster; refractive index 2.177; optically biaxial.
IMA symbol Tlr, grandfathered status — known before the IMA’s founding, named in 1845.
An alteration product of tellurium and tellurides in the oxide zone of some hydrothermal mineral deposits.
It is found associated with Tellurium, tetradymite, nagyagite, many secondary tellurates.
The name refers to its composition as a TELLURium dioxide.