796 



SCIENCE. 



[N. S. Vol. XIV. No. 360. 



Both these minerals form at the smelter of 

 the Butte and Boston Consolidated Mining 

 Co. , at Butte, Montana. They form slowly, 

 attaining their maximum thickness of 

 about four inches in the course of six 

 months to a year. They form in the Allen- 

 O'Harra calciner along the rails in the bed 

 of the furnace. In fact, they not only form 

 beneath the flanges of the rails, but also 

 slowly replace the rails themselves. When 

 the rails are taken out they have only a 

 thin upper surface layer of iron remaining ; 

 all the rest has been transformed into 

 ehalcopyrite and bornite, with the excep- 

 tion of that portion of the rails completely 

 embedded in the brick bed of the furnace. 

 An examination of these sulphides shows 

 that, while they are somewhat impure from 

 mechanically admixed quartz and perhaps 

 some other foreign matter, they exhibit the 

 true characters and chemical composition 

 of ehalcopyrite, coated in places with films 

 of bornite. Both minerals have been formed 

 by sublimation, and not by fusion, since the 

 temperature of the furnace never rises high 

 enough to fuse the ores present. Since 

 these minerals replace and destroy the iron 

 rails of the calciner, their formation leads 

 to the necessity of removing and replacing 

 the rails with new ones once every ten or 

 twelve months. 



'Note on the Minerals Associated with 

 Copper in Parts of Arizona and New 

 Mexico ' : Geo. H. Stone. 



In the mountain ranges of southeastern 

 Arizona and southwestern New Mexico are 

 numerous copper-bearing veins in lime- 

 stones and shaley limestones of Carbonifer- 

 ous age. In respect to the kinds of copper 

 compounds and the occurrence of quartz 

 and hydrous gangue minerals, these veins 

 are not very different from the copper-bear- 

 ing veins of Colorado and the States north- 

 ward. Fluorspar is rare, and the sulphates 

 scanty. It is in respect to the kind and 

 quantity of their anhydrous silicates that 



they are notable. One of the common 

 gangue minerals is pyroxene. Occasionally 

 it occurs as distinct and easily recognizable 

 four-sided needles. Generally it forms 

 small columnar or stellate crystallizations 

 that are scattered through the decomposed 

 and partially replaced lime rock, or it may 

 be enclosed in quartz. Sometimes it forms 

 slabs of asbestos up to two inches in thick- 

 ness having their fibers parallel and at 

 right angles to the surface of the slab. In 

 a few cases I noticed these slabs having 

 their fibers interlaced in all directions, and 

 then they are very tough and elastic. The 

 pyroxene occurs both in limestones and in 

 porphyry dikes that penetrate the lime- 

 stones. Asbestos occurs as a gangue mineral 

 at Ward, Boulder County, Colorado, and 

 in some others of the mountain districts, 

 but I have never seen it so abundant as in 

 the Chiricahua range in Cochise County, 

 Arizona. Another common mineral in the 

 veins in question is epidote. It occurs fill- 

 ing small cavities both in limestones and 

 porphyries, and is very common as a 

 product of contact metamorphism. But 

 now and then it occurs in large quantities 

 as gangue material proper. Thus in the 

 California Mining District in the Chiricahua 

 mountains there is a copper-bearing vein 

 which for nearly a mile is composed of a solid 

 mass of epidote wherever it has been opened 

 by cuts and shafts. It is of various widths 

 up to 5 feet. By far the most abundant of 

 the anhydrous silicates in these veins is 

 garnet. It is generally green, but occa- 

 sionally brownish or yellowish green, and 

 sometimes carmine or rose red. The copper 

 is sometimes found impregnating the garnet 

 mass, but more often occurs in porous quartz 

 alongside of the larger garnet bodies. The 

 garnets occur in irregular masses in the 

 limestone, and often line drusy cavities. 

 They are plainly a replacement of the lime- 

 stone due to vein metamorphism of the 

 country rock. In parts of the Chiricahua 



