NOTES ON THE TOPAZ FROM MINO. 



73 



The axial ratio is 



a : b: c = 0.528356 : 1 : 0.475587. 



Of the six different kinds of pyramids, ?/-, o, i, v, r, and x, the first 

 two occur most frequently, u being generally larger than o. The 

 faces r, v, and x are never found in large crystals ; they have, how- 

 ever, been observed in ten out of three hundred smaller specimens. 

 The pyramids appear more etched than the other faces. 



Among macrodomes, d is the commonest, and h is only oc- 

 casionally observed. 



Among brachydomes, / is generally present, and in many cases 

 well developed. The face y is less frequent ; and occurs only in 



1. Xokscharov ; Materiellen zur Mineralogie Russlands. 



2. loc. cit. 



3. Groth, Zeitschr. f. Kryst. u. Min. 1889. 



