142 TRAVIS— PYRITE FROM CORNWALL. [June 22 



type the " trisoctahedral type." While 'a number of trisoctahedrons 

 have been described on pyrite, their occurrence is usually scattering, 

 one or two from each locality, and not in a complete series, as in the 

 present case. 



It will be noticed that the general shape of the crystal as indi- 

 cated by Fig. I approaches a sphere, pointing to growth under great 

 pressure. 



Fig. 6. Type IL 



Type II. 



This type affords larger and more perfect crystals, which often 

 attain a diameter of 2 or 3 cm. In habit the crystal is a combina- 

 tion of cube and pyritohedron (210) with the octahedron, the diploid 

 (321) and the trapezohedron (211) commonly occurring. The cube 

 is striated in the usual manner for pyrite, parallel to the intersec- 

 tion with (210), and the (211) face is striated parallel to its inter- 

 section with the octahedron. Large natural etching figures are com- 

 mon on the cube, approximately square, in diagonal position. There 

 is reason to believe that the striation on (211) is due to natural 

 etching and not to growth. The pyritohedron has growth figures 

 as shown in Fig. 6. With the exception of the cube and trapezo- 

 hedron the faces are in general fresh and lustrous. 



A series of seven crystals was measured, and the following forms 

 observed. Those marked (*) are new for pyrite. In addition, two 

 forms (15. 1 1.7) and (i 1.8.5) have been previously observed from 

 but one locality, — Porkura.^ 



^B. Manritz in Groth's Zeitschrift, Vol. 39 (1903), p. 357- 



