Jrom the Tilly Foster Iron Mine. 455 
ing the crystalline grains in like position, and therefore being 
simultaneous in their reflection of light to the eye. 
ese magnetite pseudomorphs are often buried under ser- 
pentine, while at the same time the serpentine has sometimes a 
crust of dolomite. Hence their formation was succeeded, sooner 
or later, by other chemical depositions, that of serpentine, and 
afterward that of dolomite. 
14. Magnetite Pseudomorphs after Chondrodite and other 
Minerais. 
The whitish and greenish serpentine derived from the altera- 
tion of chlorite and other minerals has sometimes a black or 
extremely minute. The cubic ea eciades described on page 
375 has over it spots of blue-black which a 
gin. One large erystal of chondrodite (1:8 inches long), coa 
with magnetite, was covered with some of this black serpentine, 
and probably its own magnetite and that of the serpentine were 
deposited at the same time. In other cases of such second: 
deposits, besides the magnetite in fine grains there are distinct 
magnetite crystals, and even those of large size. 
Ebelmen has shown * that when carbonate of lime is brought 
into contact with a silicate of iron heated to fusion, magnetite is 
deposited. At the Tilly Foster iron mine, carbonate of lime- 
* Comptes Rendus, xxxiii, 555. 
