328 Spodumene and its Alteration*. 



as a result of the decomposition of Spodumene-crystals,, some- 

 times nine inches in width." 



Goshen Variety (Aglaite). — At the two Goshen localities, I 

 obtained a small supply of a mineral, pseudomorphous after 

 Spodumene, at once suggest ng the Cymatolite of Shepard, but 

 presenting some differences in physical character in the variety 

 found on the Barrus farm. It there occurs only as the continu- 

 ation of the imperfect square prisms of Spodumene (neve] 1 as a 

 crust upon them), in masses sometimes six* or eight inches long, 

 and from \ to | inch square, with usually a sharp line of de- 

 marcation across the prism between the two minerals. The 

 structure is micaceous, with the lamination flat, very rarely un- 

 dulating, and always in the plane of the orthodiagonal cleavage 

 of the original Spodumene crystal. The lamina? are brittle, but 

 the thinner scales are flexible, somewhat elastic, and transparent. 

 The mineral is often more or less interlaminated with Muscovite 

 and stained by Pyrolusite. Many of the lamina?, both of Agla- 

 ite and Muscovite, project \ of an inch or more into the gangue 

 at the sides of the crystals, so that the form of the prism is 

 hardly retained in the pseudomorph. Lustre between that of silver 

 and satin. Color, white. Feel, soft. Hardness=1.5. Sp. 

 (j}r.=2.753 (determined on 6 grammes). 



The specific gravity in this case, as well as in all others sub- 

 sequently given in this paper, was determined on the mineral 

 in coarse powder, in distilled water at 62° P., generally after 

 previous digestion on a steam-bath until the complete expulsion 

 of all air-bubbles. 



I am also iudebted to the kindness of Prof. 0. II. Shepard for 

 a small fragment (0.7 gramme) from one of the specimens origi- 

 nally found, by him, which, besides presenting physical charac- 

 teristics identical with those described above, was found to 

 possess a specific gravity of 2. 720. 



Chesterfield Variety. — At the Chesterfield locality, this pseu- 

 domorphous material is far more abundant, and indeed predomi- 

 nates in quantity over that both of Spodumene and of all other 

 products of alteration. The sizes of these pseudomorphs have 

 been aheadv described. Here the structure is intermediate be- 



