THE HALOID COMPOU 



b (010), c (001), m (110), e (Oil), p (111), d (110) ; Twinning plane 

 110; Cleavage, b perfeet, 101 imperfect; liritile, fracture con- 

 rlK.idal: H. = 3-3.5; G. = 3.75-3.77; Color, various shades of 

 given; Streak, apple-green; Luster vitreous ; Transparent to trans- 

 lucent; Optically ( ); Plane of the optic axes parallel to 100; 

 Bx a parallel to 4. 



B.B. Fuses on coal, yielding an azure-blue flame, and in R. F. 

 yields malleable copper buttons. In the closed tube blackens 

 and yields water. Easily soluble in acids. 



General description. Crystals are slender prisms striated 

 lengthwise and usually terminated by the unit pyramid and brachy- 

 dome ; more often massive, fibrous, or granular. First discovered 

 as a sand associated with the copper ores in the province of Ata- 

 cama, Chili. Occurs in dry regions associated with other copper 

 minerals in Tarapaca, Bolivia; Wallaroo, Australia ; and at Jerome, 

 Arizona ; but only in Chili does it occur in quantities sufficient to 

 constitute an important copper ore. 



CARNALLITE 



Carnallite. Potassium and magnesium chlorides ; KC1. 

 MgCl 2 .6H 2 O; K = 14.1, Mg = 8.7, Cl = 38.3, H 2 O = 39.0; 

 Orthorhombic ; Type, Didigonal Equatorial ; & : b : c = .5935 : 1 : 

 .6906; 100 A 110 = 30 41', 001 A 101 = 49 19', 001 A 011 = 

 34 37', 001 A 111 =53 32'; Common forms, c(001), m(110), 

 p(lll); Cleavage, none: Fracture conchoidal, brittle; H. =1; 

 G. = 1.60 ; Color, white or reddish ; Streak, white ; Luster, greasy ; 

 Transparent to translucent; Deliquescent; Has a bitter taste; 

 Optically (+) ; Plane of the optic axes parallel to ft; 2E = 115 1. 



B.B. Easily fusible, yielding a violet flame (K). With S. Ph. 

 bead saturated with copper oxide an azure-blue flame (Cl). After 

 ignition on coal leaves a residue which becomes flesh-colored when 

 treated with cobalt solution. Easily soluble in water, the solution 

 having a bitter taste. 



General description. Usually massive, deposited in layers 

 interbedded with salt and kieserite (MgSO 4 . H 2 O), and associated 

 with sylvite and kainite, both of which may be derived from the 

 carnallite, as percolating waters containing magnesium sulphate 



