i9o6] TRAVIS— PYRITE FROM CORNWALL. 139 



A detailed description of the fifteen crystals measured is un- 

 necessary, but several crystals will be taken up in detail to give an 

 idea of the relative prominence of the observed forms. 



Crystal ^ is a typical crystal illustrating (952). It is a fragment, 

 less than half of a complete crystal, about 4 mm. long. It shows 

 one end of a cubic axis, with parts of four octahedron faces and Jtwo 

 (210) faces, the larger of the latter being 3 mm. by 1.5 mm. and the 

 other about half that size. One trisoctahedron face is present ; if 

 the larger pyritohedron is called (102) this trisoctahedron will be 

 (122). It is about 0.5 mm. wide. The face (529) appears cutting 

 off the corner at the junction of (102), (122) and (m). It is 0.5 

 mm. by o.i mm. and very perfect and bright. 



Crystal 10 may be taken as typical of those showing the various 

 trisoctahedrons well developed. It is a fragment about 5 mm. in 

 diameter. It shows two complete pyritohedron faces each about 2 

 mm. wide. If we put them in the position of (102) and (102) re- 

 spectively, the other faces developed will be these, — about half of 

 (021) and a small part of (021). The zone (210), (Too) and {210) 

 appears, showing a small fragment of these faces. This is the only 

 appearance of the cube on the crystal. The octahedron appears as 

 small portions of the four upper faces. Three trisoctahedron zones 

 appear, (221) being most prominent and giving faces about i mm. 

 wide. 



One of these zones shows two small faces occupying the position 

 of (552) or (331) ; they are too minute to give a reflection. The 

 next zone is rich in faces. Starting with the octahedron having the 

 position (ill), we have in order, (iTi), (566), (122), (377) on one 

 side, and on the other (255), (122), (Hi). The two (221) faces 

 are about 0.5 mm. wide; the other trisoctahedrons uniformly about 

 0.1 mm. The third zone is similar, but shows two faces of (552) 

 instead of one of (552) and one of (773), and a face of (443) in- 

 stead of (665). 



Two diploid faces are present, in the positions (529) and 

 (7.3.13). The face of (952) is extremely small and bright, and cuts 

 off the corner formed by (102), (iii), and (122). The face of 

 (13.7.3) is larger, — i mm. long by 0.2 mm. wide, — and rounds off 

 into the adjacent octahedron face, the rounded part being a conical 



