364 Schaller — Siderite and Barite from Maryland. 



Art. XXXIII. — Siderite and Barite from Maryland; by 

 Waldemar T. Schaller.* 



Siderite. 



A number of specimens of small splendent crystals of sider- 

 ite were obtained through the courtesy of the Foote Mineral 

 Company of Philadelphia, who give as the locality, " within 

 two miles of Frostburg, Maryland." The crystals are very 

 small and are deposited in great numbers on a gray massive 

 siderite rock. A very striking feature of the crystals of sider- 

 ite is the splendent play of colors that they show. They 

 are very iridescent, and while their color is brown, the light 

 reflected from the surfaces of the crystals is in all colors. Asso- 

 ciated with the siderites and intermingled with them are numer- 

 ous small barite crystals. The matrix is a compact impure 

 iron carbonate having a specific gravity of 3*7. In this are 

 imbedded occasional masses of white, opaque barite showing 

 good cleavage. In the rock are numerous cavities which are 

 lined with siderite and barite crystals, the specimens forming 

 geodes, the crystals having been derived from the massive rock. 



The crystals vary in size from those which are very minute 

 to those a millimeter in size. They are mostly attached to the 

 matrix by one end, though double terminated crystals are by 

 no means rare, these being irregularly scattered through the 

 mass. The entire layer of crystals is about a millimeter thick. 



Chemical Properties. — A number of the crystals were 

 broken from the specimens and very carefully selected from 

 the matrix by hand. The crystals were freed from a small 

 amount of barite by the electromagnet and finally about one- 

 tenth of a gram of pure crystals was obtained, of which each 

 crystal had been picked out and shown to be free from any 

 foreign matter. It was noted that the crystals did not possess 

 a uniform color, some of them being a much lighter brown 

 than others. It was at first thought that the lighter colored 

 ones contained calcium or magnesium, but such was found not 

 to be the case. The change in the intensity of the brown color 

 of the crystals cannot be solely due to the amount of iron in 

 the crystals. The selected crystals were dissolved in hydro- 

 chloric acid and the iron precipitated with ammonia and 

 weighed. Tests made for maganese, calcium and magnesium 

 showed them to be absent. The weighed iron oxide was fused 

 with sodium bisulphate, reduced and titrated with potassium 

 permanganate, giving practically the same figure. 



* Published by permission of the Director of the U. S. Geol. Survey. 



