Thenardite: The mineral thenardite information and pictures

About

Thenardite is a delicate sulfate mineral that comes from arid dry or saline lake deposits. It is similar to Mirabilite, a chemically similar mineral to Thenardite that, unlike Thenardite, contains water in its structure. Mirabilite is an unstable mineral, and will dehydrate and lose its water when exposed to air, thereby changing to Thenardite. These altered specimens are in fact 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), a professor at the University of Paris.

Crystal Forms & Aggregates

As intergrown clusters of distorted crystals, oftenbipyramidal in shape. Individual crystals, which are rare, are tabular and short prismatic. Sometimes in well-formed twinned crystals that bisect each other. Also massive, grainy, encrusting, and in coral-like masses.

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.

Striking Features

Weak taste and fluorescence

Environment

Dry lakes and saline lakes in evaporite deposits, mainly in arid regions.

Noteworthy Localities

Thenardite has come from 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. Thenardite 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.

Common Mineral Associations

Halite, Borax, Ulexite, Colemanite

Distinguishing Similar Minerals

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

Thenardite

Abouti

Crystal Forms & Aggregatesi

Other ID Marksi

Striking Featuresi

Environmenti

Noteworthy Localitiesi

Common Mineral Associationsi

Distinguishing Similar Mineralsi

Photos