214 Reéxamination of American Minerals. 
a constant composition, and it was only after a series of analyses 
that he obtained any concordant results. The specimens he 
examined were both crystallized and foliated, the folia in some 
cases overlying the crystalline portion. With this explanation the 
composition he obtained is easily understood. 
The following are the results of our analyses. Nos. 1 and 2 
were foliated. Nos. 3 and 4 were of the radiated variety. 
a 2: a: 4, 
Magnesia, 66°30 66:25 42:30 4400 
Protoxyd of iron, ‘50 ‘ 1-00 trace trace 
* manganese, trace trace trace 
Carbonic acid, 1-27 trace 36:74 3660 
ter, 31:93 32:75 20°96 19-40 
Direct determination of water, 20°10 
The foliated variety gives the exact composition of Brucite. 
In two determinations of loss by heat, the numbers 34-30 and 
35°67 were obtained ; great difficulty was found in obtaining the 
Brucite perfectly pure owing to its intimate association with 
hydro-magnesite. ie 
The radiated variety (as before stated) gives the composition! 
of hydro-magnesite, and to show that the original analyses were 
made froma mixture of these minerals, we give Dr. Enni's te 
sults* for comparison. 
Mg Fe é i Total. 
0-01 1-01 27-07 21:60 9969 
50°72 96 26°85 21:47 10000 
9. Hydro-magnesite found crystallized. 
The hydro-magnesite above mentioned is extremely beantifl, 
and in appearance resembles very much the Thomsonite from Kil- 
patrick in Scotland. Its structure is highly crystalline and 10 some 
instances forms distinct crystals, which have been considered 38 
monoclinic? (Dana); the diagonal cleavage is very distinct. Hane 
ness 3-3-5 (scratching calcite with ease). Sp. Gr. 2-145-2'18- 
oceurs at Wood’s Mine, Texas, Lancaster County, Pa., 10 8 1g 
which are sometimes half an inch in thickness, and at er 
Mine in veins, generally from one-tenth to one-fifth of ani 
wide, having a beautifully radiated structure. The results 
two analyses of a specimen from Wood’s Mine are as follows: 
. 
Magnesia, 43:20 42:51 
Carbonic acid, 36-69 P| a oe 
Water, 20°11 S076 
* From Dana’s Mineralogy, p. 213. 
