SUU'llATis, CHRQMATE8, ITC. 535 



The base is usually rough and uneven. It is more often granular 

 nr massive. 



Kainite beinji very soluble in water has Ix-m deposited from con- 



centrated sea water; when this concent rat ion has reached the 



where the sulphates have heeil deposited and the mother 



liquor is saturated in respect to the chlorides and sulphates, 

 douhle salts are separated, of which kainite is an example. This 

 mineral, however may have been formed by the interaction of car- 

 nallite ( K( '1 . MgCl 2 ) .6 H 2 O and kieserite (MgSO 4 ) . H 2 O as a 

 ndary mineral. 



Kainite is found in quantities at the unique salt deposits of 

 Sta>sfurt and in small deposits of the same character in Galicia. 

 These two deposits are of great commercial value, as they furni>h 

 the potash supply to the world, and which is essential as one of the 

 necessary plant foods, so apt to be early exhausted from the soil. 



HANKSITE 



Hanksite. -^4 Na 2 SO 4 INaaCOs double salt found under the 

 same conditions as kainite, and interesting as one of the few miner- 

 als illustrating the dihexagonal equatorial type. Its crystals are 

 tabular combinations of the base, unit pyramid, and prism. It is 

 found associated with the borax lake deposits of California. 



MIRABILITE 



Mirabilite. Hydrous sodium sulphate, NaaSCh . 10 H 2 ; 

 Na,< ) = 19.3, SO 3 = 24.8, H 2 O = 55.9 ; Monoclinic ; Type, 

 Digonal Equatorial ; a:b:c = 1.1158: 1: 1.2372; p = 72 15' = 

 001,100; 100,110 = 46 44'; 001,101 =57 55'; 001,011 = 49 

 41' ; Common form, a (100), b (010), c (001), m (110) ; Cleavage, 

 a perfect, c and b in traces; H. = 1.5-2; G. = 1.48; Color and 

 streak, white ; Luster, vitreous ; Transparent to opaque ; |J = 1.44 ; 

 Optically (-); Axial plane _L 010; Bx. = b ; 2E = 12248'. 



B.B. Boils and yields a yellow flame (Na). In the closed 

 tube yields much water. After ignition leaves an alkaline residue. 

 Very soluble in water, the solution yields a white precipitate with 

 barium chloride (BaSO 4 ). Has a cooling, bitter taste. 



General description. Occurs as crusts or in beds in the de- 

 posits formed by the evaporation of salt lakes. Sodium sulphate 

 is contained in varying amounts in all natural waters; upon con- 



