50 Brush and Dana—Fairfield County Minerals. 
An analysis of a carefully selected specimen by 8. L. Pen- 
field gave 
Silica 49°22 
Alumina 17°58 
Tron sesquioxide 1:99 
Manganese protoxide 0°56 
Lime 6°73 
Potash 2°83 
Soda 1°44 
Water 17°83 
Quartz ats 
100-96 
RHODOCHROSITE. 
It will be seen from what has been said in this and in our 
first paper, that rhodochrosite is a very common mineral in its 
association with the phosphates. In the first deposit it occurred 
sometimes in specimens of large size with the characteristic 
color and cleavage (RAR = 106° 49’), and again in granular 
aggregates interpenetrated with quartz, and often taking a 
greenish color from the dickinsonite. It also appears altered 
to a black, highly lustrous mineral, containing only the oxides 
of iron and manganese. 
_ In the deposits which form the special subject of this paper, 
the rhodochrosite occurs first of a pink color implanted in the 
S Mean. Ratio. 
CO, 37.78 37°80 37°8 *859 1 
FeO 16°74 16°78 16 76 “233 
MnO 44°68 44-50 44°59 *628 867 1 
CaO 0°33 0°33 0°33 006 
MgO tr. tr. tr. ” 
Insoluble 0-35 0°29 0°32 
99°88 99°70 99°80 
The variation in color of the mineral implies that the com- 
position varies widely, which would doubtless be shown, could 
analyses of different varieties be made. The interest connected 
with the subject is, however, small, although the large amount 
: Pages 
of iron present is worthy of no 
See 
Pee ret 8 a (Sem) ~ A Ren a ee ao 
