90 On Columbite and other North American Minerals. 



remaining in my possession, but without finding the substance 

 which I supposed Berzelius alluded to ; and since that time, 

 until lately, I had made no other search for it. A few weeks 

 since, however, in examining some splendid specimens of the 

 above-mentioned remarkable rock, presented to me by Col. 

 Gibbs, I observed disseminated through one of them, several 

 small masses of a blackish substance, having the appearance 

 of an ore of Manganese. On a more attentive examination, it 

 presented some unusual characters, and at length I discovered 

 a considerable number of minute crystals, which were evident- 

 ly of the same mineral with the masses. It occurred to me 

 that this was the Tantalite of Berzelius, and a chemical exa- 

 mination of the small portion of the mineral which I could sa- 

 crifice for this purpose, left little doubt on the subject. The 

 following is a more particular description of the mineral. 



It occurs in small amorphous masses, and in minute crys- 

 tals, disseminated in a granitic aggregate, consisting of quartz, 

 albite,* talc, friable manganesian garnet, beryl, cymophane, 

 &c. The amorphous masses, which are probably very imper- 

 fect crystals, are from one-fourth to half an inch in diameter, 

 of a grayish-black colour, with the surface always more or less 

 irised. It is opaque. Its structure is imperfectly foliated. Its 

 fracture is somewhat conchoidal. It is not magnetic, either 

 before or after being heated with charcoal. It is sufficiently 

 hard to scratch glass, but not to strike fire with steel. The 

 powder of the mineral is very dark brown. Specific gravity 

 5.90. Before the blow-pipe it is nearly infusible, the smallest 

 fragment being slightly rounded on the edges. Borax dis- 

 solves it very slowly, forming a pale yellowish glass. 



* Ci.eavelandite of H. I. Brooke, Esq. as proposed in the last edition 

 of Phillips 1 s Mineralogy. It is a subject of regret, that this name must be 

 given up for that of Albite, the latter having been severaLyears since pro- 

 posed by Hisinger and Berzelius for those varieties of Feldspar having a 

 base of soda. 



