SUI. I'll ATI'S, rilHu.MATKS, ETC. 539 



Kieserite, MgSO 4 .H 2 O, is a maum -slum sulphate containing only 

 one molecule of water. It is iiionorlinir and iinich less soluble 

 than cpsoinitc, hut dissolves slowly in water and rerrystallizes as 

 i I>M, mite at ordinary tern perat urea. Kirscrite separates from solu- 

 t ions above 68 C. Kieserite is associated with carnallite and gyp- 

 sum at the Stassfurt salt deposits. Here it has Iwen separated from 

 solutions containing sodium and potassium salts, and under then- 

 conditions a number of double salts have been formed, as blodite, 

 N.iM- S() 4 ) 2 .4H 2 O; loweite, Na 2 Mg(SO 4 ) 2 . 2 H 2 O ; picromerite, 

 KjMg(SO 4 ) 8 .6HsO. 



Isomorphous with epsomite is the zinc sulphate, goslarite, 

 ZnS( ) 4 . 7 H2O, derived from the oxidation of sphalerite and 

 occurring on the walls of old mine workings; also morenosite, 

 NiSO 4 . 7 H 2 O ; the nickel sulphate is a member of the same 

 group. 



Commercially magnesium sulphate is separated at the Stassfurt 

 works. It is used in medicine as a purgative, and as a coating for 

 cotton cloth in dyeing. 



MELANTERITE 



Melanterite. Copperas ; Ferrous sulphate, FeSC>4 . 7 H 2 ; 

 FeO = 25.9, S0 3 = 28.8, H 2 O = 45.3; Monoclinic; Type, 

 Digonal Equatorial; a: b: c == 1.1828: 1 : 1.5427; P = 75 44' = 

 001,100; 100,110 = 48 54'; 001 , 101 = 43 44' ; 001,011 = 

 56 13'; 111,111 = 78 33'; 001,110 = 80 41'; Common 

 forms, b (010), c (001), m(110), r(lll), o(011), v(101); Cleavage, 

 basal perfect, m less so; Brittle; Fracture, conchoidal; H. = 2; 

 G. = 1.89-1.90; Color, shades of green to yellow; Streak, white ; 

 sul transparent to translucent; a= 1.471; (3 = 1.478 ; -y = 1.485; 

 y - a = .014; Optically (+) ; Axial plane = 010; Bx a ,c = 62 

 28' behind; 2V = 88 48'. 



B.B. Fuses and blackens, leaving a magnetic residue on coal, 

 which reacts only for iron with the fluxes. In the closed tube 

 yields water. Soluble in water ; the solution acidified with HC1 

 yields a white precipitate with barium chloride ; yields a sulphur 

 reaction with soda on silver. It has an astringent, nutallic taste. 



General description. Crystals are short, prismatic in habit, 

 but the salt in nature is usually fine fibrous, massive, or concretion- 

 ary. The yellow color of some specimens is caused by oxidation 



