Formula: V4+O(SO4).3H2O
Hydrated sulphate, vanadium-bearing mineral
Specific gravity: 2.28 calculated
Hardness: 1
Streak: Pale blue
Colour: Pale blue, blue-green

Hydrothermal environments

Bobjonesite occurs as crusts and efflorescences. It hydrates rapidly on exposure to air, and is stable only in the driest atmospheres (Mindat).


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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