502 Mineralosrical Notices 



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bate of lime, according to one of Shepard's analyses, con- 

 firmed. Dana's Mineralogy, one of the arrangements of 

 which is crystallographical, although in the last edition, 

 entering into every other possible detail on these two miner- 

 als, singularly enough omits even an allusion to the above 

 circumstance, notwithstanding its being so remarkable an in- 

 stance of the power of crystallography to indicate error in 

 chemical analysis, even in hands like those of Wohler. 



This mineral is an excellent exemplification of the difficul- 

 ties which at present surround the natural arrangement of 

 minerals, although chemical analysis is, unquestionably, here- 

 after destined to be its basis. The analyses of the dark- 

 colored crystals give, as ingredients, columbic acid, lime, 

 manganese, iron, tin, lead, uranium, &c. ; whereas the mi- 

 nute transparent yellow crystals are probably pure columbate 

 of lime, or, perhaps, even obtaining their color from a slight 

 admixture of oxide of uranium, as this color diflfers much, in 

 intensity, in crystals of the same size. These small transpa- 

 rent crystals are generally modified on the edges and solid 

 angles of the octohedron ; in the large, dark-colored crystals, 

 these modifications are often nearly obliterated. 



My largest crystal of Pyrochlore, from the Chesterfield 

 locality, is f of an inch at the base of the octohedral pyramid. 



CoLUMBiTE is usually described as of a dark, opake, sub- 

 metallic, iron-black color. I possess a small crystal of this 

 substance, from Chesterfield, of a brilliant, transparent, dark 

 ruby red. I name this subject, because, as in the previous 

 instance of Pyrochlore, the small, transparent crystals of 

 minerals are usually most free from adulteration, and the 

 fittest to produce the true atomic formula on ^hemical analy- 

 sis. The excellent observations of Rammelsberg on this 

 whole subject are well worth the attention of all mineralogists. 



PYROPHYLLITE and VERMICULTTE. 



In the paper before alluded to, published in the proceedings 

 of this society, I have stated tlie probabiHty of the identity 

 of these two minerals. 



