Goldschmidt mid Nicol — New Forms of Sperrylite. 451 



The nine crystals measured showed the following combina- 

 tions : 



Combinations. 

 } . g* e . b* . . m q . p u . . . 



s • • e p . . . . 



;..e qBp.... 



i. . e.b"d.mqBpui/>x. 

 : . . e . . d k . q . p u f . . (z) 

 ; . . e h 



Fig. 2. 



Crystal No. 1 

 Crystal No. 2 

 Crystal No. 3 



Crystal No. 4 : 

 Crystal No. 5 : 

 Crystal No. 6 . 



Crystal No. 7 

 Crystal No. 8 

 Crystal No. 9 



From this table of combinations the relative frequency and 

 importance of the individual forms can be observed. 



Fig. 3. 

 Fig. 4, 

 Fig. 5. 



c . 

 c a 



d k m q 

 . . . q 



(D) 



The following arrangement shows the relative importance : 

 e always present, usually predominating. 

 p almost always present, usually smaller than e, sometimes of 



equal importance with c, now and then predominating. 

 e always present, but less important by far than p, 

 q o u m very small, but occurring not seldom, 

 ag'hb* kBx occurring seldom and unimportant. 

 z D scarce, faint and uncertain. 



Up to the present time, from the measurements of Fen field 

 and Walker, the following forms were known : 



c = 0(001); 6=10(101); e = + \ (102) ; p = 1 (111). 



These are, in fact, the most important forms. In addition 

 "Walker gives the form \\ (5.2.10), determined from measure- 

 ments of plane angles. This form was not found on any of 

 the nine crystals measured. It lies in the zone + \ q, between 

 e = -J-0 and q = -J, — an important zone for this mineral. It 

 may perhaps be identified with the form i/r = \\. In the same 

 zone lies the uncertain form D = -|4 and the well defined form 

 u = i 1. Figures 2, 3, 4 and 5 show crystals Nos. 1, 4, 5 and 

 6. Fig. 1 gives an ideal picture of all the forms. Owing to 

 the difficulty of drawing so many narrow faces and reproduc- 



Am. Jour. Sci. — Fourth Series, Vol. XV, No. 90. — June, 1903. 

 31 



