AI(T. '23 



DURANGO MINEIJALOGY AND GEOLOGY — FOSHAG 



11 



Range ^^ describes several different forms of hematite, including 

 the compact, specular, and earthy hematite. Pie says '^ that, while 

 it was at one time believed that magnetite was present in considerable 

 quantities in the deposits, careful search has demonstrated its essen- 

 tial absence. He believes tliat a certain amount does occur at Picacho 

 Socavon 2 but in minor amounts. An analysis of the ore from this 

 point shows 4.88 per cent of ferrous iron equivalent to 5.24 per cent 

 of magnetite, and this is the largest amount thus far reported from 

 the deposit. In general appearance and in magnetic effects this 

 ore comes nearest to magnetite of any mineral yet reported. Small 

 octahedrons and masses that are 

 strongly magnetic are scattered 

 thi'ough the altered wall rock and can 

 be properly classified as magnetite. 



Apatite. — Clear, glassy apatite crys- 

 tals (92153) are not uncommon in 

 man}- parts of the hill, where they are 

 called "' a7??a?*?7/(75 " (yellows) by the 

 minei's. They may be found in small 

 numbers at Penascos de la Industria, 

 in greater numbers and finer crystals 

 at Cueva de la Marmaja, at various 

 places in Socavons Nos. 1 and 2, and 

 on tlie northern slope of the hill. 

 Their color is a clear lemon yellow. In 

 form they are hexagonal prism modi- 

 fied by narrow faces of the second- 

 order prism and terminated by the six faces of the unit hexagonal 

 P3a-amid. (Fig. 2.) The largest crystals observed by the writer are 

 two presented by Seiior Rangel to the collections of the United States 

 National Museum and to the Holden collection of the Harvard Min- 

 eralogical Museum and which measured 4 centimeters in diameter 

 and 5 centimeters long. Many of the crystals are sufficiently clear 

 and flawless to be cut into semiprecious gem stones. 



The apatite crystals are found in several different modes of occur- 

 rence; most commonly in small crystals in the cavities of compact 

 martite ore at Penascos de la Industria Avhere it is associated with 

 martite crystals or more rarely imbedded in the massive ore. At 

 Cueva de la Marmaja they are found in small veinlets in the soft 

 ore and it is from here that the better grade of " amarUJas " come. 

 In Socavon 1, they are associated with quartz and chalcedony and 

 are always broken and imbedded in light masses of sepiolite. In the 

 older workings on the north slope of the hill the apatite crystals are 



Fig. 2. — Crystal Habit of Apatite 



" Inst. Geol. de Mexico, vol. 16, p. 6, 1902. 

 " Oral communication to the author. 



