58 Chemical Examination of American Minerals. 



of Dr. Langstaff's prior experiments, I examined the mineral 

 called Brucite by Colonel Gibbs, having been informed that it 

 was the filiate of magnesia alluded to b^ Professor Cleaveland. 

 My analysis was read before the Lyceum of Natural History. 

 I obtained about 4 per cent of fluoric acid, and 50 per cent 

 of silica, an ingredient which 1 did not expect to find, at least 

 in such large proportion, so that it proved to be a fluo-sili- 

 cate, analogous, as I stated in my memoir, to the topaz. 

 While I was repeating my analysis, with a view to its publi- 

 cation, I was informed that Dr. Langstaff had already exam- 

 ined the mineral, and had anticipated my results. I therefore 

 prosecuted the subject no farther, and solicited the discoverer 

 of the mineral himself to give the public an account of his 

 experiments. As no account of the Sparta mineral had been 

 published in 1821, when Professor Cleaveland was preparing 

 a new edition of his work, 1 sent him a short description of 

 it, under the name of Brucite, together with a history of its 

 discovery. By that time some of our mineralogists learned 

 from their Swedish correspondents, that the Brucite and 

 chondrodite were supposed to be identical, but as D'Ohsson 

 and Berzelius found no fluoric acid in the latter mineral, the 

 Brucite was regarded by Colonel Gibbs and others, as a dis- 

 tinct species. 



In May 1822, and before Cleaveland's second edition ap- 

 peared, Mr. H. Seybert, of Philadelphia, read before the 

 American Philosophical Society, an account of the New- 

 Jersey mineral, to which he gave the name of Maclurite. 

 He appears to have been unacquainted with the experiments 

 made on this substance in New- York, and also with the fact, 

 which was already well known to the mineralogists of this 

 city, that Berzelius had pronounced the chondrodite and 

 Brucite to be the same species, but without (it would appear) 

 having detected any fluoric acid in either mineral. The 

 analysis of Mr. Seybert displays great ingenuity and science. 

 He obtained the fluoric acid, and determined \tith great ac- 



