S. L. Penfield — Chalcopy rite from Chester Co., Pa. 209 



the positive sphenoid, or not. The faces are usually very little 

 rounded or distorted by the striations and in the majority of 

 cases have an inclination of ip^cp — about 25° measured over 

 the base with a contact goniometer, agreeing closely with a J- 

 sphenoid, which is the inclination given in the figure. The 

 scalenohedron ^ is also much striated, and by placing the arms 

 of a contact goniometer along the longer and shorter pole 

 edges in a number of cases it was found that they made angles 

 of about 140° and 90°, agreeing with the form 122, 1-2, in 

 which the pole edges would meet at angles of 141f° and 87|- , 

 and which is the symbol given to these faces in the figure. It 

 is possible, however, that the faces are really pyramids of the 

 second order which have been distorted by oscillatory combina- 

 tions with the positive unit sphenoid 111. A basal plane, 

 which is not shown in the figure, is frequently developed. A 

 slight modification of this type is represented in fig. 4, where 

 the <p and ^ faces are about equally developed. When the 

 basal planes, c, are present they are always striated parallel to 

 their intersection with the negative sphenoid 111 as in the fig- 

 ure. When the base is absent the crystals look almost exactly 

 like the hemihedral form of the isometric trigonal-trisoctahe- 

 dron x (122) i(2), and there is no appreciable difference in the 

 appearance or inclination of the <p and ^ faces. 



On some of the crystals the positive and negative sphenoid 

 p, 111, 1 and jo', 111, —1, are well developed and give sharp 

 reflections, while they also oscillate with other faces, giving rise 

 to striation. Fig. 5 is intended to represent these crystals, a 

 number of which were measured in hopes of finding definite 

 symbols for the sphenoids and scalenohedrons. Measuring from 

 p, 111 over the base on to p, 111, no distinct reflections were 

 observed except from p and e, but on continuing the revolution 

 of the crystal on the goniometer beyond p, 111, there immedi- 

 ately followed an unbroken band of signals without any interrup- 

 tion or prominent parts between^? and m 110. From this it may 

 be assumed, that in all probability, the striated phenoids (p are 



