76 



schaller: immense bloedite crystals 



sulfate with 1.66 per cent MgO. In the black mud below this 

 crust were found the isolated crystals of bloedite — a hydrous 

 magnesium-sodium sulfate with 12 per cent MgO. 



The larger crystals have a dark almost black appearance 

 when the superficial covering of grey mud is removed tho the 

 smaller crystals are nearly colorless, the black appearance being 

 due to impurities. In places the larger crystals are likewise 

 nearly colorless and translucent and in small pieces transparent. 

 In fact, selected fragments are clear and glassy and together 

 with the lack of cleavage, greatly resemble quartz fragments. 



The largest crystal at present on hand measures 16^ cm. (6^ 

 inches) by 10| cm. by 3| cm. and weighs 652 grams. The crys- 

 tals are flattened somewhat parallel to the base and show the 

 following forms: 



Large c(OOl), d(Oll), m(llO) 



Medium ._ ._.... .n(210), p(lll) 



Small 5(201), s(211), u(lll), a:(121) 



The measurements were made with a contact goniometer and 

 gave the following results: 



FORM 



m(llO) 



c(OOl) 



c(OOl) 



n(210) 



TO (110) 



d(Oll) 



c(OOl) 



c(OOl) 



:p(_lll)... 



:g(201)... 

 :p{in)... 

 : n"'{210). 

 : m"'(110). 

 :d'(0il).. 

 :s(211)... 

 : M(lll)... 



The form x(121) was determined by zonal relations. 



An analysis of selected pure material gave the following: 



Analysis of bloedite from California 



H2O 21 .37 ■ 



MgO 11 .93 



Na^O 18.26 



SO3 ■ 48.11 



99.67 



These proportions are close to those required by the formula 



Na2Mg(S04)2.4H20. 



