Gaylussite

Gaylussite is a mineral, a hydrated sodium calcium carbonate, formula Na2Ca(CO3)2.5H2O. It is formed as an Evaporite from non marine waters. Discovered in 1826, it is named after Gay-Lussac, the French scientist.
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(n.)
A yellowish white, translucent mineral, consisting of the carbonates of lime and soda, with water.
  

General Information:
 Chemical Formula:
Na2Ca(CO3)2·5(H2O)
 Composition:
(Molecular Weight = 296.15 gm)
Sodium 15.53 % Na
Calcium 13.53 % Ca
Hydrogen 3.40 % H 
Carbon 8.11 % C 
Oxygen 59.43 % O 
 Empirical Formula:
CaNa2(CO3)2·5(H2O)
 Name Origin:
Named after the French chemist and physicist, J. L. Gay-Lussac (1778-1850).
Physical Properties:
 Cleavage:
[110] Perfect, [001] Indistinct
 Color:
colorless, gray, gray white, yellow, or yellowish white.
 Density:
1.93 - 1.99, Average = 1.96
 Diaphaniety:
Translucent
 Habits:
Disseminated - Occurs in small, distinct particles dispersed in matrix., Tabular - Form dimensions are thin in one direction.,
 Hardness:
2.5 - Finger Nail
 Luminescence:
None.
 Luster:
Vitreous (Glassy)
 Streak:
white
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