22 



S. L. Penfield — Pearceite, a Suljpharsenite of 



The following table of measured angles includes a series 

 whicli was selected wholly on account of the character 

 of the reflections, due to the freedom of the faces 

 from striations and other disturbing influences. They were 

 mostly made on the two fragmentary crystals, already men- 

 tioned, having a habit like fig. 2, and where several measure- 

 ments are given they represent independent ones in different 

 zones or on different crystals. As may be seen, the measured 

 angles show a fairly good agreement with the calculated values, 

 and it may, therefore, be assumed that the axial ratio has been 

 determined with a fair degree of accuracy. 



Calculated, 



e /s a, 001/^100 

 c /^l, 001/s310 

 G ^'m, 001 /s 110 

 m /\m, 110/sllO 

 b /sm, 010^110 

 a /s I, 100/v,310 

 b ^ /i, 010,' 1=^^ 



b ^7c, 010/^02 

 c /v cl 001 /v 10-^ 



^ d, 001^..- 

 n. 001/slOl 



c 

 c 



G 



71°, 001^101 



/s e°, 001^401 



d y\r, 



t% 001/^201 



O ^/> -. 1 ,^ 7 



001^112 

 001/slll 

 102/^112 

 b ^p, OlOxsUl 

 b ^ji?°,OlO/v,Ill 

 b ^ s, 010/^221 

 001/s313 



2/5 



89' 



60 

 30 

 29 

 10 

 17 

 25 

 43 

 104 

 118 

 136 

 43 

 61 

 36 

 40 

 40 

 33 

 47 



51' 

 52 



55i 



2 



1 

 59 

 54 



9 



3 



2 

 49 

 00 

 49i 



3 

 49 

 14 

 15 



12 

 9 



Measured. 

 89° 51'*, 



89 48, 



89 55 



60 2* 

 30 1, 

 29 58, 

 10 53 

 17 5 

 25 3*, 

 43 4, 



104 58| 



117 56 



136 52^ 



43 3," 



61 56 

 36 12, 

 40 12, 

 40 8 

 33 12 

 47 10, 



89° 



49' 



89 



54 



30 



1 



29 



5H 



25 



24 



43 



5 



43 



6 



43 







36 



16 



40 



12 



47 



In the following table the calculated angles of most of the 

 faces on to the basal plane are given, arranged so as to show 

 the slight variation from one another and from rhombohedral 

 symmetry of the forms d, o smd 0° / J and q° ; n, r, n° and 



r° ; t^ ^, f and p° ; v and v^ ; e, s, e° and s° and f, u,f° 

 and tc°. 



c^d = 25° 3' 



c^o =25 3 



c^o° = 25 4^ 



c.^ A =32 



c^q° = Bl 58 



c A w =43 2 



c^r =43 3 



n 



43° 10-i-^ CaV 



70° 19' 



c^r" = 43 7i 



c^t =61 46i 



c^p =61 49 



c^r = 62 00 



Cy.p° = 61 56 



CaV°= 70 27 

 c ^e =74 54 

 c^s = 75 00 



c^e° = 75 11 

 CaS° = 75 6 



c^f = 79° 45' 



c^u =79 49-^ 

 Ca/° =80 2 



Cy^u° = 19 58 



c^z =15 6i 

 c^y = 47 9 



c A X =72 44 



Physical properties. — Fearceite is brittle, has an irregular 

 to conchoidal fracture and no distinct cleavage. The hardness 



