152 On Columbiie. 



decisions arising from crystallographic examinations with well defined 

 crystals. 1 have not, however, found the discrepancy in the specific 

 gravity, noticed by Dr. Thomson. A fragment of a crystal weigh- 

 ing about 52 grains, afforded by one trial 5.95, and by a second, 

 6.948 for its specific gravity, which is a near approach to that of the 

 Bodenmais Columbite, which is stated at 6.038. Mr. Hatchett obtain- 

 ed, for the American specimen in the British Museum, 5.918. The 

 specific gravity was determined by Dr. T. at 4.8038. There is, 

 however, as stated by Dr. T. a very evident difference in hardness. 

 I have found it to vary from 5 to 5.5. The Haddam and Middle- 

 town specimens afford a dark reddish brown, or brownish black 

 streak, and very frequently present the blue, reddish or yellowish 

 tints of the steel tarnish. 



The composition of the Bodenmais and American Columbite has 

 been variously stated by different analysts. The following are the 

 results of analyses by Borkovvsky, Vogel, Thomson and Wollaston : 



Torrelite, from 

 Bodenmais. Bodenmais. Middletown, Con. Bodenmais. Connecticut. 



CoUimbic acia, - 74.0 75 73.90 79.65 ' 80 



Proloxyd of iron, 20.0 17 15.65 14.00 15 



Protox. manganese, 4.6 5 8.00 7.55 5 



Oxyd of tin, ' 0.4 1 0.50 — 



Water, . . — ^=99 B.— =98 V. 0.35=97.9 T. 0.05=101.75 T— =100 W. 



The last analysis by Wollaston, was made with but 5 grains of the 

 original specimen in the British Museum. The results of these 

 analyses are not so widely different as to excite a doubt respecting 

 the correctness of the conclusions from crystallographic considera- 

 tions. 



There is yet much uncertainty with respect to the identity of the 

 Finland Tantalite with the species Columbite. Its superior specific 

 gravity, (7.2 to 7.3,) and slightly different composition, seem to re- 

 quire their separation. Gustav Rose, in his Elements of Crystal- 

 lography,* p. 168, has proposed this separation on crystallographic 

 grounds, and has included, as above, the Bodenmais and " Massa- 

 chusetts" (Connecticut?) specimens in the species Columbite, and 

 those from Finland under the separate name of tantalite. It would 

 appear, however, that he was not acquainted with the crystallization 

 of the American specimens ; for he arranges the species Columbite 



* Elemente der Krystallographie nebst einer tabellarischen Uebersicht der 

 Mineralien nach den Krystallformen. 174 pp. 8vo. with 10 copper pis. Berlin, 

 1833. 



