164 



RE-EXAMINATION OF AMERICAN MINERALS. 



perfectly parallel to the alternate edges, as seen in figure 4. 

 Every crystal in the group is thus furnished with a set of crys- 

 tals of pyrites. 



In another group of crystals the pyrites, in equally small 

 crystals, are found in three lines on the summit of every crystal 



Fig. 4. 



Fig. 5. 



running from the apex toward the edges, exactly bisecting each 

 face, as seen in figure 5. 



In this instance, as well as in the former, the pyrites are 

 inserted entirely beneath the surface of the crystal, which is 

 perfectly smooth. 



The calcite is found in large crystals in dolomite, and is 

 associated with most of the ores of the mine. It sometimes 

 gives rise to pseudomorphs of molybdate of lead and carbonate 

 of lead. These pseudomorphs are mere shells, however, retain- 

 ing the form of the calcite. 



64. Sulphur. 



Sulphur occurs in the form of small pale greenish-yellow 

 crystals. They are transparent and disseminated through 

 cellular galena, which appears to have undergone partial de- 

 composition. The galena in which it occurs is frequently 

 associated with copper and iron pyrites, and in some rare 

 instances with carbonate and phosphate of lead. 



The other minerals occurring in the Wheatley Mine are 

 finely crystallized quartz, oxide of manganese, iron pyrites, sul- 

 phate of baryta, indigo copper, black oxide of copper, and dolomite. 



Of the other mineral veins in this region none have yielded 

 the beautiful mineral species furnished by the Wheatley vein. 

 The Perkiomen vein, five miles from the Wheatley vein, has 

 furnished fine capillary copper, indigo copper, fine acicular crys- 

 tals of sulphate of baryta, crystallized copper, and some crystals 



