CAVE MATERIAL FROM A MEXICAN MINE 



By Edmund Otis Hovey 



THE department of geology has received from Mr. Grant B. Schley, 

 president of the El Potosi Mining Company, a series of remarkable 

 specimens of calcite and aragonite (carbonates of lime) and selenite 

 (sulphate of lime) from a cave in the company's mine near the city of 

 Chihuahua, ^Mexico. This cave consists of a series of chambers in massive 

 limestone and was broken into in the course of ordinary mining opera- 

 tions. The rooms are on several levels and are of different heights, al- 

 though there are none with ceilings very lofty. 



The calcite and aragonite show some most delicate tints — water 

 white and snow white, rose, salmon color, light lemon and sulphur yellow. 



One of the chambfrs of the cave discovered in a mine near Chiluialiua. Delicate 

 and fantastic crystals from tliis cave are on exhibition in the hall of historic geology 



The selenite or gypsum occurs in transparent, colorless crystals and crystal- 

 lized aggregates, and as thick mats of long slender crystals resting like 

 glistening snow upon curiously distorted helictites of the carbonate of lime. 

 Radiating arrow heads of calcite are grouped together in some of the speci- 

 mens and blunt crystals in others, but the most showy group of all consists 

 of slightly salmon-colored, double-pointed two-inch crystals of dogtooth 

 spar forming a flat mass more than thirty inches across. 



Unfortunately for science and the public, the cave contains a large 

 amount of valuable silver lead ore in its walls and floor and is now in 

 process of demolition for the winning of the precious minerals. 



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