132 



TRAVIS— PYRITE FROM CORNWALL. 



[June 22 



Type I. 



In habit Type I is a combination of (iii) and (210), (m) 

 being more developed. The pyritohedron (210) appears in all 

 degrees of development from tiny triangular faces at the corners of 

 the octahedron to equilibrium with it. The trisoctahedron (221) is 

 common and seems to vary with (210), those crystals that have a 

 small pyritohedron face having little or no trisoctahedron. This is 

 not, however, true in all cases. The cube is comparatively rare. 



Fig. I. Type L 



The faces in general are fresh and brilliant. Crystals from the 

 weathered portions show a brown tarnish, which is removed by hot 

 hydrochloric acid, leaving the crystal as bright as fresh material. 

 The octahedron is striated parallel to its intersection with (210) and 

 (221), producing six-sided figures. The pyritohedron has growth 

 figures on its surface, in the form of curved isoceles triangles, whose 

 sides are apparently the intersection of (210) with all possible tris- 

 octahedrons from (221) to (m). 



The cube, when present, is the most perfect face on the crystal, 

 and is absolutely without striation. This may be partly due to the 

 fact that it is never very large, and is usually a narrow face beveling 

 the edge of the pyritohedrons. Fig. i illustrates the general habit 

 of Type I, and makes an attempt to show the striation and growth 

 figures. The crystals of Type I are, in general, small, few exceeding 

 0.5 cm. in diameter. 



On a series of fifteen crystals of Type I the following forms were 

 observed. Those marked (*) are new for pyrite, and one (14.11.8) 

 has been reported from but one other locality, namely Kotterbach.^ 



^K. Zimanyi in Groth's Zeitschrift, Vol. 39 (1903), p. 125. 



