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THE GUIDE TO NATURE. 



II. PYRITE FROM CENTRAL CITY, COLORADO. 



slightly tapering" and terminated by 

 pyramids which show an abnormal de- 

 velopment of three alternate faces, al- 

 most eliminating the other three. The 

 chalcopyrite crystals are deeply im- 

 planted among the spires of quartz ; 

 and though the former fit tightly 

 around the latter, and even partly en- 

 close them, in no case are quartz crys- 

 tals found implanted in the chalcopy- 

 rite, in this specimen. This proves to 

 us that the quartz is of the first gen- 

 eration, and the chalcopyrite of the 

 second, that is, that the quartz formed 

 before the chalcopyrite. 



III. PYRITE FROM FRANKLIN, NEW JERSEY. 



Chalcopyrite crystals very similar to 

 these have been found elsewhere. Many 

 of the English specimens are very fine, 

 the crystals being, in many cases, large 

 and untarnished. Some years ago, 

 mines at Ellenville, N. Y., produced 

 some very fine large chalcopyrite crys- 

 tals, which were associated with 

 quartz crystals, as in the English 

 specimens. Many of the Ellenville 

 chalcopyrites, though often associated 

 with quartz crystals of considerable 

 size and beauty, were so badly tar- 

 nished as to be almost black, which 

 detracted much from their beauty. 



The tiny tetrahedrons of chalcopy- 

 rite, on dolomite, which come from the 

 vicinity of Joplin, Missouri, are well 

 known to all who are familiar with 

 minerals. A number of very fine ones 

 of larger size have been found at the 

 French Creek Mines, in Chester Co., 

 Pa., now long since closed. Chalcopy- 

 rite is found in a great many places, 

 and in its usual massive form is an im- 

 portant ore of copper. It is the prin- 

 cipal ore of copper at the Cornwall mines. 

 II. Pyrite, Central City, Colorado. 



In the handsome group of cubes here 

 shown we have a typical example of 

 pyrite as found in the state of Col- 

 orado. It is a group of cubes, very 

 simple in form and perfect in develop- 

 ment, with faces typically striated. The 

 cubes are promiscuously scattered over 

 a matrix composed of the same min- 



