296 [February, 



very probably exists in the form of a basic lime salt, similar to compounds well 

 known in mineralogy. 



In order to test the correctness of the opinion that fossil bones contain fluoride 

 of calcium in larger proportion than recent ones, the fluoride of calcium was 

 determined with the greatest care. In no instance, however, was so large a 

 quantity found as in the analyses of fossil reptiles by Baumert,* where the 

 quantity of fluoride of calcium in the Zeuglodon macrospondylus amounts to 

 9-54 per cent, and in the Hydrarchos even to 16'67 per cent. By direct deter- 

 mination, Heintzf found the quantity of fluoride of calcium in two human bones 

 to be 2*97 and 2-05 per cent ; the former of which corresponds almost exactly 

 with the quantity found in the dentine of Titanotherium. In the tibia of the 

 Archaeotherium, a portion of the fluoride of calcium may have been introduced 

 in the same manner as the quartz and sulphate of baryta. 



The Committee on the following papers by Dr. Grenth, reported in 

 favor of Publication. 



On a new variety of Gray Copper , perliaps a new mineral* 



By Dr. F. A. Genth. 



Massive, apparently without any crystalline structure. H=4-5 ; Sp. Gr. ? ; 

 color nearly iron-black, when in very thin splinters subtranslucent with cherry- 

 red color ; streak brownish red ; lustre sub-metallic ; fracture sub-conchoidal ; 

 brittle. 



B. B. fuses readily=l ; gives off" the odor of arsenic and sulphurous acid, 

 leaving incrustations of antimony and zinc ; with carbonate of soda on charcoal 

 yields a globule of silver and copper. Soluble in nitro-hydrochloric acid with 

 separation of chloride of silver. 



The analysis gave the following composition : 



43 



25.48 



100.00 



It is found at McMackin's Mine, Cabarras County, N. C, but rarely, and is 

 associated with Iron Pyrites, Galena, Blende, Talc and Carbonate of Magnesia. 



The sulphur ratio of the sulpho-bases and sulpho-acids is =11.43 : 14.05 



= 1: 1.23 



corresponding with the formula 5 (Ag, Cuj, Zn Fe) S-f-2 (As, Sb) S3. 



I had, as the data of the analysis will show, but a very small quantity of the 

 mineral, and, therefore, although this formula is that of a new mineral, I am un- 

 willing to give it a new name, until more of it will be found, and the analysis 

 repeated ; at present it is preferable to consider it as a variety of gray copper, 

 whose composition is expressed by the formula 4RS4-RS3. 



The following are the methods and data of the analysis : 0.1330 grs. were 

 dissolved in nitro-hydrochloric acid, and the chloride of silver filtered after di- 

 luting with a large quantity of water. It gave 0.0140 grs. metallic silver. The 

 filtrate was evaporated almost to dryness, and heated with sulphite of soda ; and, 

 after in this manner the arsenic acid had been reduced to arsenious acid, the ex- 

 cess of this reagent decomposed by hydrochloric acid. A current of hydro- 



* Liebig und Kopp, Jahresbericht fiir 1851, p. 594. 

 t Pogg. Ann. V. 77, p. 267. 



