CALIFORNIA ACADEMY OF SCIENCES. 371 



of which is 15 mm. long by 8 mm wide, the smallest 5 mm long 

 by 2 mm. wide. The habit of the_crystals is strikingly different 

 from the Cornwall and Cransac crystals, in that all of the nega- 

 tive terminal forms are entirely wanting, bringing about a pro- 

 nounced resemblance to a familiar gypsum form. The forms ob- 

 served are: b = oo 3? oo, parallel to which most of the crystals are 

 tabular, a = oo P go quite fully developed on some, m = oo P small, 

 v = P, and io = P oo, which are the principal end forms. In 

 Fig. 12, PI. IV, two other forms are represented, about which I 

 am doubtful. u is in the zone v (P): a (oo Poo), but it is so 

 small and reflects so poorly that but a rough approximation to its 

 true inclination to v or a can be obtained. I found v : u = 141 , 

 with a possible error of several degrees. I have drawn u in the 

 figure as 4 P 4, the inclination of which to v is 146° 56'. It is 

 not quite clear that t is in the zone of the brachydigonal polar 

 edge of u, although I have drawn it so, making t = 4 P oo. 



Azurite from Diana Mine, Mono County, California. 



In 1880, Mr. Stewart, a former student at the University, was at 

 the Diana mine, when one of the miners brought up from below a 

 fine slab of limonite, a foot and a half in length and half as 

 wide, thickly studded on one side of delicate deep blue azurite 

 crystals. The slab was broken before Mr. Stewart could prevent 

 it, but one of the fragments was presented by him to the Univer- 

 sity Collection, The crystals of azurite are all very small, and 

 grouped in cellular aggregates, or singly implanted in the massive 

 limonite. The habit is rectangular-tabular, parallel to o P, the 

 tables being extremely thin and elongated in the direction of the 

 ortho-diagonal. Fig. 13, PI. IV represents one of these tables 

 2.0 mm. long, 0.G3 mm. wide, and 0.09 mm. thick. The com- 

 bination consists of h = o P ( 001 ), a = \ P oo ( 102 ), 

 / = \ P oo ( 012 ), p = P a> ( 011 ), M = oo P ( 110 ), 

 k = — P(lll). 



The reflections from h and a were very good, so that the angle 

 fe:o = oP:JP oo= 132° 56' 10", agrees closely with the cal- 

 culated value, 132° 54'. The basal pinacoid is delicately striated 

 parallel to the edge h : f. The other faces are so exceedingly 



