Yellow crystals of the very rare Se-U mineral larisaite associated to metallic acicular native selenium crystals, on a contrasting matrix. From: Repete Mine, Blanding, San Juan County, Utah, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Larisaite
Larisaite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Na(H₃O)(UO₂)₃(Se⁴⁺O₃)₂O₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group Pm).
Key properties: Mohs hardness 1; specific gravity 4.46; Yellow streak; Vitreous; pearly on cleavage surfaces. Green fluorescence in UV luster; optically biaxial.
IMA symbol Ls, IMA status: approved, named in 2002.
Found as a secondary mineral in an oxidized ‘roll-front’ U deposit in sandstone.
It is found associated with Montmorillonite, quartz, haynesite, wölsendorfite, andersonite, uranophane, gypsum, calcite.
The mineral was named to honor Russian mineralogist Larisa Nikolaevna Belova (1923-1998) for her studies of U minerals.