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Formula: Na(H3O)(UO2)3(Se4+O3)2O2.4H2O
Hydrated selenite, uranyl mineral
Crystal System: Monoclinic
Specific gravity: 4.46 calculated for the empirical formula and 4.50 calculated for the ideal formula
Hardness: 1
Streak: Yellow
Colour: Canary-yellow
Luminescence: Fluorescence under UV is green (Excitation wavelength 250 nm)
RADIOACTIVE
Environments
Larisaite was approved on 2002 but to date (July 2024) it has been reported only from the type
locality.
Localities
At the type locality, the Repete Mine, Montezuma Canyon Mining District, San Juan County, Utah, USA, larisaite
occurs as a secondary mineral in sedimentary rock. It forms
coarse lamellar crystals up to 1 mm in size and rosettes up to 2 mm, in cracks, in association with
montmorillonite, quartz,
haynesite, wölsendorfite,
andersonite, uranophane,
gypsum and calcite.
Crystals of larisaite are transparent or translucent, canary-yellow, with a vitreous lustre and pearly sheen
on cleavage planes
(EJM 16.2.367-374).
Larisaite from the Repete Mine -
Image
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