Ottoite
Ottoite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Pb₂TeO₅.
It crystallizes in the monoclinic crystal system (space group I2/a).
Key properties: Mohs hardness 3; specific gravity 8.721; Pale yellow streak; Adamantine luster; optically biaxial.
IMA symbol Oto, IMA status: approved, named in 2009.
A secondary phase on fracture surfaces and in small vugs in quartz veins. Formed from the partial oxidation of primary sulfides (e.g., galena) and tellurides (e.g., hessite) during or following brecciation of the quartz veins.
It is found associated with Acanthite, bromine-rich chlorargyrite, gold, iodargyrite, khinite, wulfenite, housleyite, markcooperite, thorneite, timroseite.
The name is derived from the locality, Otto Mountain, California, USA.