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Thenardite Floater Crystal

The Mineral thenardite

The mineral Mirabilite is a very similar mineral to Thenardite but contains water in its chemical structure whereas Thenardite does not. Mirabilite is an unstable mineral and when exposed to air it will dehydrate and lose its water, thereby converting to Thenardite. These specimens are really Thenardite pseudomorphs after Mirabilite. Some of these crystals, especially those of outstanding crystal form, are artificially grown as by-products of borax mining operations.

Thenardite is named after the French chemist Louis Jacques Thenard (1777-1826), who was a professor at the University of Paris.
Chemical Formula Na2SO4
Composition Sodium sulfate
Color White, yellowish, light brown, gray
Streak White
Hardness 2.5 - 3
Crystal System Orthorhombic
Crystal Forms
and Aggregates
Occurs as intergrown clusters of distorted crystals. Individual crystals, which are rare, are tabular and short prismatic. Sometimes occurs in well-formed twinned crystals that bisect each other. Also occurs massive, grainy, encrusting, and in coral-like masses.
Transparency Transparent to translucent
Specific Gravity 2.7
Luster Vitreous
Cleavage 1,1 - basal
Fracture Uneven to hackly
Tenacity Brittle
Other ID Marks 1) Has a weak salty taste.
2) Slowly soluble in water.
3) Fluorescent white in shortwave ultraviolet light and yellow-green in longwave ultraviolet light; may also be phosphorescent.
In Group Sulfates; Anhydrous Sulfates
Striking Features Weak taste and fluorescence
Environment Dry lake deposits and saline lakes in desert regions.
Rock Type Sedimentary
Popularity (1-4) 3
Prevalence (1-3) 2
Demand (1-3) 2

Thenardite AUCTIONS

Thenardite occurs in evaporite deposits in arid regions. It is found in Espartinas, Spain; Mt. Etna, Vesuvius, Italy; the Bilma Oasis, Niger; and Wadi el Natrun, Egypt. In the U.S., it occurs as sharp, twinned crystals in Soda Lake, San Luis Obispo Co., California. It also occurs in other dry lake deposits in California, including Searles Lake, San Bernardino Co.; Boron, Kern Co.; and Borax Lake, Lake Co. It also has come from the Verde Valley, Yavapai Co., Arizona.

Halite, Borax, Ulexite, Colemanite

Glauberite - Less soluble in water, forms different crystals.
Halite - Much saltier taste, occurs in different crystals, has perfect cubic cleavage.

thenardite PHOTOS
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