88 



distinguished from it in hand specimens. It is associated with 

 Brucite, but is very scarce. Mr. A. gave his reasons for con- 

 sidering Dysluite as identical with Aiitomalile, They pass into 

 each other, and the differences in hardness, color, specific gravity 

 and pyrognostic characters, can thus be accounted for by the 

 well-known fact of the isomorphous replacement of the constitu- 

 ents of certain m.inerals, the crystalline forms of which remain 

 the same. Specimens are seen, in which the bright and perfect 

 crystals of Automalite gradually lose their lustre, and become 

 porous, brittle and soft ; thus assuming the characters of Dysluite. 



Oitrelite^ of MM. Desclozeaux and Damour, identical with 

 Phyllite, of Dr. Thomson. This fact was pointed out by Mr. A. 

 on the grounds of similarity in chemical composition, as well as 

 in physical and crystallographical characters, so far as these latter 

 have been determined. They both occur in small disks or plates, 

 very thin, and the most perfect of them having the form of com- 

 pressed or flattened rhomboidal tables. A specimen of Ottrelite, 

 which he had received from Mr. Markoe, and another of Phyliite, 

 from the hands of Prof Nuttall, enabled Mr. A. to compare them 

 carefully with each other ; and he had no hesitation in declaring 

 them to be the same mineral. Damour's analysis shows the iron 

 to be in the state of protoxide ; and it, probably, exists in the 

 same state in Phyliite, though it is put down as peroxide in Dr. 

 Thomson's analysis. The name Ottrelite should give place to 

 that of Phyliite, on the ground of the priority of the latter, and 

 because it expresses so well the ordinary appearance of the min- 

 eral. Brooke had supposed Phyliite to be identical with Gigan- 

 tholite. If we compare the analyses of Gigantholite and Ottrelite, 

 their identity is much more clearly shown, so that it would appear 

 that all three should be classed together. 



Polyadelphite. Mr. A. remarked that Dana, in the new edition 

 of his mineralogy, had included this mineral under the species 

 garnet. The correctness of his opinion was now further shown 

 by the circumstances of its occurrence at the locality which Mr. 

 A. had visited the last year. The two minerals occur together, 

 and pass into each other, in the same manner as Dysluite and 

 Automalite. It differs but little in composition, compared with 

 the brown garnet from Franklin, analyzed both by Dr. Thomson 

 and Seybert. 



I 



