SEARLESITE

    Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Monoclinic
    Chemistry : NaBSi2O5(OH)2
    Rarity : Rare

Searlesite is a rare sodium-boron silicate that forms in a variety of environments. Although it is favored in salt lake deposits and continental borate evaporites, it is also reported from phonolite geodes (Point of Rocks, New Mexico) and alkaline syenites (Kola, Russia). It was named for John W. Searles, a California pioneer who discovered Searles Lake. Searlesite can form colorless flat crystals up to 17 cm long, but it more commonly forms radiating aggregates of acicular or prismatic crystals, as well as granular masses.

Main photo : Searlesite from Point of Rocks Quarry, New Mexico, USA © Michael C. Michayluk

Searlesite from Coaldale Mining District, Nevada, USA © Gianfranco Ciccolini
Twinned supposed searlesite from Rio Tinto, California, USA © Gianfranco Ciccolini
Twinned supposed searlesite from Rio Tinto, California, USA © Jason B. Smith
Searlesite on aegyrine from Point of Rocks Quarry, New-Mexico, USA © Jerry Cone

Searlesite in the World

The best searlesite crystals come from a layer of trona interstratified in oil shales and maerls of Sweetwater County (Wyoming). It is also present in California, in the large Kramer borate deposit near Boron, and in the deposits of several salt lakes : Searles, its definition site (which provided white spherulites 1 mm in diameter), Tecopa and China. In the Silver Peak Mountains (Nevada), it presents crystals of 3 mm. Searlesite seems rare outside the United States, known only in a few Russian localities (Caspian salt depression, Lovozero alkaline syenite...), Yugoslav and Bosnian (Lopare).

Searlesite in France

Searlesite is not present in the French underground.

Twinning

No twinning officially described for this mineral species, but many crystals seem to have contact twins.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3.5
Density : 2.44 to 2.46
Fracture : Undertermined
Streak : White

TP : Transparent
RI : 1.516 to 1.535
Birefringence : 0.019
Optical character : Biaxial -
Pleochroism : None
Fluorescence : Green

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None

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