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Formula: V4+O(SO4).3H2O
Hydrated sulphate, vanadium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.28 calculated
Hardness: 1
Streak: Pale blue
Colour: Pale blue, blue-green
Environments
Hydrothermal environments
Fumeroles
Bobjonesite occurs as crusts and efflorescences. It hydrates rapidly on exposure to air, and is stable only in the
driest atmospheres
(Mindat).
Localities
At the First scoria cone, Northern Breakthrough, Great Fissure eruption, Tolbachik volcano, Kamchatka Krai, Russia,
bobjonesite occurs as a sublimate at an active volcanic fumarole. Associated minerals include
markhininite,
shcherbinaite,
pauflerite, karpovite,
evdokimovite and microcrystalline magnesium, aluminium,
iron and sodium sulphates
HOM).
At the type locality, the North Mesa Mine group, Temple Mountain, San Rafael Mining District, Emery County, Utah, USA,
bobjonesite occurs in a silicified tree, that has a rim of coal 6–25 mm thick around it.
Pyrite has replaced part of the tree, and groundwater has reacted with the
pyrite to produce various iron sulphate minerals, including
ferricopiapite, kornelite,
rozenite and szomolnokite,
accompanied by microscopic yellow crystals and yellow-to-green fine-grained aggregates of native
sulphur. The iron sulphates generally occur in the outer rim of coal and in
the adjacent conglomerate. There is dense submetallic to
somewhat earthy, dull grey, radiating montroseite in the silicified tree,
the probable source of the vanadium that occurs in blue and green
secondary vanadium sulphate minerals; these include
bobjonesite, anorthominasragrite,
orthominasragrite and
minasragrite
(CM 41.83-90).
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