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Formula: MoO3.H2O
Oxide of molybdenum, paramorph
of raydemarkite
Crystal System: Monoclinic
Specific gravity: 3.71 measured, 3.69 calculated
Hardness: About 2
Streak: White
Colour: Pale yellow-green in transmitted light
Solubility: Insoluble in water or hydrochloric acid
Environments
Virgilluethite is a new mineral, approved in 2023 and to date (December 2023) reported only from the
type locality.
Localities
At the type locality, the Summit group, Cookes Peak Mining District, Luna County, New Mexico, USA,
virgilluethite was found on a specimen in an unnamed short adit. All virgilluethite crystals are
pseudomorphs after
sidwillite, apparently resulting from the topotactic dehydration (loss of
interlayer H2O molecules) of sidwillite. All crystals of
virgilluethite greater than 10 microns in length occur as aggregates of sub-parallel plates. Furthermore, some
aggregates are also intergrowths of virgilluethite and
tianhuixinite. Associated minerals are
sidwillite, raydemarkite,
tianhuixinite, ilsemannite,
jordisite, powellite,
fluorite, baryte,
pyrite and quartz.
The Summit group of claims is rich in fluorite in many places. Hydrothermal
solutions originating from a granodiorite produced ore bodies
localised in limestone units beneath impermeable
shales which were subsequently accompanied by silicification, the latter
leading to the formation of jasperoid (a dense, usually gray, chert-like
siliceous rock, in which chalcedony or cryptocrystalline
quartz has replaced the carbonate minerals of
limestone or dolostone)
(CJMP 61.6.1151-1162).
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