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Chemical Formula | Na2SO4 |
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Composition | Sodium sulfate |
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Color | White, yellowish, light brown, gray |
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Streak | White |
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Hardness | 2½ - 3 |
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Crystal Forms and Aggregates |
(Orthorhombic) Occurs as intergrown clusters of severely distorted crystals. Individual crystals, which are very 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. |
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Transparency | Transparent to translucent |
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Specific Gravity | 2.7 |
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Luster | Vitreous |
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Cleavage | 1,1 - basal |
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Fracture | Uneven to hackly |
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Tenacity | Brittle |
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Other ID Marks | 1) Has a weak salty taste 2) Slowly soluble in water 3) Fluoresces white in shortwave ultraviolet light and yellow-green in longwave ultraviolet light; may also be phosphorescent |
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In Group | Sulfates ; Anhydrous sulfates |
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Uses | Thenardite is used in the manufacture of glass and paper. |
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Striking Features | Weak taste and fluorescence |
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Popularity (1-4) | 3 |
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Prevalence (1-3) | 2 |
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Demand (1-3) | 2 |
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Distinguishing Similar Minerals |
Glauberite - less soluble in water, forms
different crystals Halite - much saltier taste, occurs in different crystals, has perfect cubic cleavage |
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Commonly Occurs With |
Halite, Borax, Ulexite, Colemanite |
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Noteworthy Localities |
Thenardite occurs in evaporite deposits in arid regions. It is found in
Espartinas, Spain; the Bilma Oasis, Niger; and Pampa
Rica, Chile. 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 the southern U.S., including Searles Lake, San Bernardino Co., California, and the Verde Valley, Yavapai Co., Arizona. |
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