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Thénardite
Current inventory:  0 gems
 

Chemistry:  Na₂SO₄  [Sodium Sulfate]

Discovered in 1826;   IMA status: Valid (pre-IMA; Grandfathered).
Thénardite is named in honor of Professor Louis Jacques Thénard (1777–1857), French chemist, University of Pierre and Marie Curie, Paris, France.

Classification

Mineral Classification:

Sulfates

Strunz 8th Ed. ID:

6/A.07-10

Nickel-Strunz 10th Ed. ID:

7.AC.25

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
A : Sulfates (selenates, etc.) without additional anions, without H₂O
C : With medium-sized and large cations

Related to:

Thénardite - Mascagnite Series

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals dipyramidal {111}, or tabular {010} with large {101}, rarely prismatic along [100], to 20 cm; as pulverulent crusts and efflorescences

Twinning:

On {110}, commonly forming cruciform groups; as crude butterflylike twins on {011}

Physical Properties

Cleavage:

[010] Perfect, [101] Fair, [100] Interrupted

Fracture:

Splintery, Uneven to Hackly

Tenacity:

Somewhat Brittle

Hardness (Mohs):

2.5 - 3.0

Density:

2.664 - 2.700 (g/cm³)

Luminescence:

Fluorescent; SW UV = white, LW UV = yellow-green

Radioactivity:

Not Radioactive

Other:

Easily soluble in water

Optical Properties

Color:

Colorless; Grayish White, pale Yellow, Yellow-Brown, Reddish due to inclusions

Transparency:

Transparent to Translucent

Luster:

Vitreous to Resinous

Refractive Index:

1.471 - 1.484  Biaxial ( + )

Birefringence:

0.0013

Dispersion:

Weak to None; r > v

Pleochroism:

None

Occurances

Geological Setting:

Typically in lacustrine (salt and soda lake) evaporite deposits in arid regions, also as crusts and efflorescences, which may be ephemeral, in a wide range of geologic environments; as precipitates around fumaroles.

Common Associations:

Blödite, Epsomite, Glauberite, Gypsum, Halite, Mirabilite, Natron

Type Locality:

Espartinas Salt Lake, Aranjuez, Madrid, Spain

Year Discovered:

1826

View mineral photos:

Thénardite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Thénardite is a rare sulfate mineral that is rarely found as crystals large enough for faceting. It is one of several arid region, non-marine evaporate sulfate minerals and is associated with other minerals that form in the deposits of playa lakes. Thénardite is readily water soluble and should be stored carefully.

There are numerous minor occurrences of Thénardite but rarely in thick beds or as large crystals. Two notable localities for relatively large crystals are from Searles Lake, San Bernardino County, California, USA and Bärenstein Quarry, Niederschlag, Oberwiesenthal, Erzgebirge, Saxony, Germany.
 

  
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