p^p, 

 p^p, 



P^P, 



c^v, 



d^r, 



Cy\ T, 



C/\ a, 



A 3 /sa, 



^ /\ A 



A sa7, 



^AV, 



CA£, 



Pen field and Frenzel — Identity of Chalcostibite, etc. 35 



Measurements obtained from pyramidal faces 

 Calculated. I. VI. 



863^863 

 863^863 

 863 : 863 

 6-12-7^6-12-7 

 6-12-7a6'12-7 

 6-12-7/s6'12-7 

 001^136 

 001^134 

 011^134 

 101^134 

 001^133 

 001^265 

 001/^263 

 001^4-12-5 

 001 A 261 

 001^233 

 205 /s 233 

 001^354 

 205^354 

 101/s354 

 001^474 

 205/s474 

 101/s474 

 001/^475 

 001^476 



VII. 



126° 21' 

 138 21 



32 16* 



69 38 

 105 19 



67 



20 



29 



16 



40 



37 



42 



56 



61 



77 



45 



126° 31' 



32 

 69 



18 

 49 



29 

 50 

 71 



92 



58 

 42 

 35 

 52 



47 



11 

 41 

 31* 



40* 



45* 



3 



11 



29 



6* 



33 



44* 



19* 



20 



2 



2 

 41 

 18* 

 34 

 45 

 37 



67 18 



126° 21'* 



138 21* 



32 16 



69 34 



105 16 



67 11* 



20 18 



30 

 16 

 40 



22 

 32* 



36 

 41 

 56 

 61 



77 



45 

 46 

 12 



8 

 32 



46° 

 30 



50 28' 



71 



92 



58 43 

 42 3 

 34 53 

 52 25 

 45 to 47° 



In the preceding tables, many of the measurements show 

 considerable variation from the calculated values, which might 

 be expected, owing to the striated character of some of the 

 faces and the small size of others. On the other hand, the 

 measurements from the best and most prominently developed 

 forms, h, d, g, u, q, andj?, show a very close agreement with 

 the calculated values, and it is believed that the axial ratio 

 which we have established is more accurate than those given 

 by other investigators. 



It is probable that the pyramid x mentioned by Friedel 

 (ex = 56° 24') lap, 6-12-7 (c^p calculated = 56° 24*0, whicn 

 is prominently developed on the crystals from Wolfsberg and 

 Huanchaca. 



In conclusion, we take great pleasure in expressing our 

 thanks to Professors Friedel and Groth, and Messrs. Cumenge, 

 Hohmann, Spencer, Schott and Fletcher, who have rendered 

 valuable assistance by supplying us with material for this 

 investigation and information concerning the mineral. 



Mineralogi cal-Petrographical Laboratory, 



Sheffield Scientific School, February, 1891. 



