Gaylussite - Encyclopedia

    Class : Carbonates, nitrates, borates
    Subclass : Hydrated carbonates
    Crystal system : Monoclinic
    Chemistry : Na2Ca(CO3)2 5H2O
    Rarity : Quite common

Gaylussite is a hydrated carbonate formed by evaporation of salt lakes. In its deposits it is associated with thermonatrite, trona, calcite and many other carbonates. It was named in honor of the French physicist and chemist Louis Joseph Gay-Lussac who established the law of gas expansion, the laws of the combination of gases in volume and who discovered boron. Gaylussite is a mineral that occurs in crystals that are often flattened and elongated, with beveled ends and usually uneven faces. It is colorless or grayish-white in color, sometimes yellowish. Usually translucent, gaylussite becomes opaque and whitens in the air ; furthermore it easily alters into calcite. It is a sodium ore.

Main photo : Gaylussite from Taboos-nor, Gobi Desert, Mongolia © Joan Rosell

Gaylussite in the World

Gaylussite is common in the salt lakes of California and Nevada, it is also common in the salt lake deposits of the Gobi Desert (China and Mongolia) and Venezuela. The large calcite pseudomorphs crystals from Helensburg (Scotland) are among the largest and most famous of this mineral species. Those of Lake Searles (California) exceed 5 cm.

Right photo : Gaylussite from Searles Lake, California, USA © Jesse Crawford

Gaylussite in France

Gaudefroyite is not present in the French underground.


No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 2.5
Density : 1.99
Fracture : Conchoidal
Streak : Gray-white

TP : Translucent to transparent
RI : 1.444 to 1.523
Birefringence : 0.079
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid and hydrochloric acid

Magnetism : None
Radioactivity : None


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