JPalache and Warren- 



-KrohnTcite, Natrochalcite. 345 



Natrochalcite, a new mineral. 



Bright emerald-green crystals of what proves to be a new 

 hydrous double sulphate of copper and sodium were found on 

 several specimens. The crystals are either isolated or in closely 

 adhering crusts upon the white vein matrix ; in one specimen 

 they are embedded in chalcanthite and doubly terminated crys- 

 tals were obtained by carefully breaking away the enclosing 

 blue vitriol. The mineral is monoclinic with a striking pyra- 

 midal habit, shown in figure 6 ; the crystals attain a length 

 of about l cm and are generally attached to the matrix in such 

 a way that portions of both prism and pyramid are developed ; 



an oscillatory striation parallel to intersection edge of these 

 forms, due to the development of steeper pyramids between 

 them, is generally well marked. A small basal pinacoid and 

 the other faces shown in figure 7, but of minute size, are 

 generally present. The faces proved to be of good quality in 

 most cases and the measurement of six crystals, mostly very 

 small and one of them doubly terminated, yielded satisfactory 

 data for calculation of the elements. For this purpose 45 

 faces of seven forms were available. 



p = -8526 q = 1-065 /x = 61° 17' 30" 



from which was calculated 



d : b : e = 1'423 : 1 : 1-214 j3 = 61° 11' 30" 



