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Gaylussite
Current inventory:  0 gems
 

  
Gaylussite is named in honor of Joseph Louis Gay-Lussac (1778–1850), noted French chemist and physicist.

Discovered in 1826;   IMA status: Valid (pre-IMA; Grandfathered).

Chemistry

Chemical Formula:

Na₂Ca(CO₃)₂·5(H₂O)

Hydrated Sodium Calcium Carbonate

Molecular Weight:

296.15 gm

Composition:

Sodium

15.53 %

Na

20.93 %

Na₂O

Calcium

13.53 %

Ca

18.94 %

CaO

Hydrogen

3.40 %

H

30.42 %

H₂O

Carbon

8.11 %

C

29.72 %

CO₂

Oxygen

59.43 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Carbonates

Strunz 8th Ed. ID:

5/D.02-60

Nickel-Strunz 10th Ed. ID:

5.CB.35

5 : CARBONATES (NITRATES)
C : Carbonates without additional anions, with H₂O
B : With large cations (alkali and alkali-earth carbonates)

Related to:

Thermonatrite - Chalconatronite Series

Synonyms:

Gaylussacite, Gay-Lussite, Natrocalcite

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Includes intricately faceted prismatic to tabular crystals, but also massive and encrusting. Crystals frequently elongated [100]; also flattened, wedge-shaped, with dominant [110], and [011]. Surfaces commonly rough, with [011] striated [111].

Twinning:

None

Physical Properties

Cleavage:

[110] Perfect, [001] Imperfect

Fracture:

Conchoidal

Tenacity:

Very Brittle

Moh's Hardness:

2.5 - 3.0

Density:

1.93 - 1.99 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Dehydrates slowly with efflorescence in dry air; slowly decomposes in water leaving CaCO3 as Calcite or Aragonite. Soluble in acids with effervescence. Slightly soluble in water. Alters readily to calcite.

Optical Properties

Color:

Colourless, Yellowish, Greyish, White; Colourless in transmitted light.

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.444 - 1.523  Biaxial ( - )

Birefringence:

0.0790

Dispersion:

Strong; r < v

Pleochroism:

None

Occurances

Geological Setting:

Typically in evaporites or shales from alkali lakes; rarely in veinlets cutting alkalic igneous rocks. Lacustrine clay sediments in an alkali lake.

Common Associations:

Shortite, Northupite, Pirssonite, Trona (Green River Formation, Wyoming, USA); Aegirine, Ferrian “Biotite”, Pectolite, Potassian Feldspar, Shortite, Thermonatrite, Villiaumite (Khibiny massif, Russia).

Type Locality:

Lagunilla, Mérida, Venezuela

Year Discovered:

1826

View mineral photos:

Gaylussite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Gaylussite is a relatively rare mineral but a very rare gem. It is one of several carbonate minerals that form in non-marine evaporite deposits. These carbonates include Trona, Pirssonite, Nahcolite, Northupite and Thermonatrite and are difficult to tell apart from each other. Optical or X-ray techniques are often necessary to identify them. Gaylussite is subject to dehydration which can cause cloudiness of gems and deterioration and therefore should be stored in a sealed container.

Notable occurrences include Searles Lake, San Berardino County; Deep Spring and Owens Lake, Inyo County; Borax Lake, Lake County and China Lake, Kern County, California, USA; Gobi Desert, Mongolia and Lagunillas, Merida, Venezuela.
 

  
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