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Formula: BaWO4
Tungstate, scheelite group,
barium-bearing mineral
Crystal System: Tetragonal
Specific gravity: 6.363 calculated
Streak: White
Colour: Colourless
Luminescence: The grains fluoresce weakly blue-white under 312 nm short wave UV
Environments
Ronpetersonite is a new mineral, approved in 2023 and to date (May 2024) reported only from the type locality.
Localities
At the type locality, the Gun claim, Wilson Lake, Itsi Mountain, Watson Lake mining district, Yukon, Canada,
ronpetersonite is hosted by a Frasnian-age (382.7 to 372.2 million years ago)
baryte bed that was subsequently mineralised with the intrusion of the Gun
pluton during the Cretaceous period (145 to 66 million years ago). The region surrounding the Gun occurrence contains
several tungsten skarn deposits.
Ronpetersonite was identified in seven anhedral, equant grains approximately 100 to 500 microns across. These
grains occur in a groundmass dominated by witherite,
cerchiaraite-(Al) and
edingtonite, and contain inclusions of
witherite and
cerchiaraite-(Al).
Other minerals found in the groundmass include diopside,
quartz, sphalerite containing
exsolved chalcopyrite, celsian
with rims of cymrite, a relict iron-rich phase,
cerchiaraite-(Fe),
taramellite, itsiite and
alforsite. Much of the
cerchiaraite in the thin section is of intermediate Fe-Al composition,
with no cerchiaraite-(Mn) present.
The major assemblage of witherite,
cerchiaraite and
edingtonite
with cymrite after celsian implies
extensive late carbonate replacement and hydrothermal alteration. The presence of these late minerals as inclusions in
ronpetersonite implies that ronpetersonite formed during retrograde hydrothermal alteration. Subsequent
overgrowth of diopside is also observed. It is likely that the Gun pluton is
the source of the W in ronpetersonite, the surrounding Ba was derived from the associated host rock, and
ronpetersonite crystallised after primary crystallisation
of anhydrous silicate minerals and during the formation of witherite and
cerchiaraite. The rarity of this mineral is likely due to the unique
requirement of both Ba and W at sufficient concentrations for the two elements to interact
(CJMP 62.2.405-415).
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