Re- examination of Microlite and Pyrochlore. 159 



I shall also leave those " rules," which separate the microlite from 

 pyrochlore, and place it with yitro-tantalite, their full influence. 

 The kindness of Mr. Teschemacher and Mr. F. Alger, has ena- 

 bled me to review my experiments on the microlite, and by placing 

 in my hands fine crystals of both microlite and pyrochlore, laid 

 me under obligation to communicate any additional information 

 my results might afford. 



I gave the pyrognostic characters of microlite, which are dis- 

 tinctive for the species, in the paper published by Mr. Teschema- 

 cher. They correspond to those of pyrochlore, so far as they 

 were known to me. Pyrochlore was considered as a titanate of 

 lime, with other oxides crystallized together. Besides the cor- 

 respondence exhibited with fused reagents, I ascertained that the 

 microlite was soluble in hydrochloric acid. The solution nearly 

 neutralized by an alkali, gave to shavings of gall-nut a red brown 

 color. When the acid solution was enclosed in a tube, with a bit 

 of metallic zinc, a bluish purple color was produced. The anal- 

 ysis of one grain was made as an addition to the chemical char- 

 acters. Some months after I made this examination, I saw for 

 the first time Prof. Shepard's paper, (Vol. xxxn, p. 338, of this 

 Journal,) giving a "chemical examination of microlite," and was 

 not before acquainted with the fact, that the statement of its com- 

 position, given on the authority of Prof. S., as an ore of cerium, 

 had been corrected. By the " examination" referred to, the evi- 

 dence that columbic, instead of titanic acid, is the electro-posi- 

 tive constituent of microlite, I consider conclusive. I therefore 

 most freely retract the opinion I expressed in relation to this 

 point, and shall show how I was led into the error. 



Analysis of the Microlite, from Chesterfield, Mass. 



Regular crystals of the microlite were broken into fragments; of 

 the parcel, about one fragment in twenty-five had a yellow color;* 

 the residue presented shades of brown. Diluted hydrochloric 

 acid was warmed on the fragments, to remove any adhering min- 

 erals. No lime or uranium was dissolved, but a little peroxide of 

 iron was contained in the solution. After washing: the fragments 



* Mr. Teschemacher has called my attention to some minute, transparent, yel- 

 low, and highly brilliant crystals, which, with columbite and microlite, are found 

 in the Chesterfield granite. They have the characters of a columbate, but differ in 

 form from microlite. Mr. T. has a crystal of microlite, much modified by an ura- 

 nium mineral, crystallized with it. Generally the yellow stains on the albite are 

 the most marked indications of the existence of microlite crystals. 



