DICKTHOMSSENITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated vanadates
    Crystal system : Monoclinic
    Chemistry : Mg(V2O6) 7H2O
    Rarity : Very rare


Dickthomssenite is a very rare mineral that forms in oxidation zone sandstones of American vanadium-uranium deposits, where solutions rich in vanadium and magnesium precipitate to form this hydrated mineral. It was named in honor of Richard William "Dick" Thomssen, an American geologist specializing in the exploration of uranium and vanadium deposits in the southwestern United States. Thomssen contributed significantly to the study of these deposits and to the collection of numerous rare microminerals from the Colorado Plateau mines. The crystals are acicular to prismatic in radial aggregates and do not exceed 2 mm. Their color ranges from white to pale yellow.


Photo : Dickthomssenite from Blue Streak Mine, Montrose County, Colorado, USA © Travis Olds

Dickthomssenite in the World

Dickthomssenite is an extremely rare mineral, known almost exclusively from the Colorado Plateau region, a vast geological area straddling Utah and Colorado (USA). The type-locality is the Firefly-Pigmay Mine in San Juan County, Utah, where the mineral was discovered in millimeter-sized crystals in association with other vanadium and uranium oxidation species. This mine remains the most emblematic and best-documented occurrence. Other nearby localities in Utah, such as the Vanadium Queen and Blue Cap mines, have also yielded dickthomssenite in millimeter-sized crystals. However, several occurrences have also been reported in similar deposits in neighboring Colorado, particularly in mines located in Montrose and Mesa counties. All of these discoveries are part of the uranium-bearing sandstone deposits typical of the Colorado Plateau, where hydrothermal circulations rich in vanadium and uranium precipitated a wide variety of secondary minerals. Outside of this Utah-Colorado region, no other significant occurrences of dickthomssenite are currently known, making these specimens particularly sought after by specialized collectors.

Dickthomssenite in France

This mineral is not present in the French underground.

Twinning

No twin reported for this mineral species.

Fakes and treatments

No fake inventories for this mineral species.


Hardness : 2.5
Density : 1.96 to 2.09
Fracture : Irregular
Trace : White

TP : Translucent to transparent
RI : 1.612 to 1.710
Birefringence : 0.098
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : None
Radioactivity : None