the Tilly Foster Iron Mines. 209 
Making for the oxygen ratio of 
, 3, 8i, H, 5°00: 2°85: 6-07: 3°92, or for RB, Si, H, 4: 3°09: 2. 
The corresponding ratios of ripidolite are 5:3:6:4 and 4: 
3:2; and hence the mineral is that species. 
xygen. 
SiO, 37°33 21°00 
Al,O, 7°58 3°53 
FeO 9°62 2°13 
MnO tr. 
MgO 33°56 13°4 
H,O 11°63 9°91 
The oxygen ratio for 
R, #, Si, H, is 16:3:21:9, orfor R, 8, 8i,H, 6:66:30 
It approaches the ratio of pyrosclerite, in which this ratio 1s 
4:2:6:8 or 6:6: It seems to be perfectly homogeneous, 
and not the result of decomposition. 
White Serpentine. —This variety is opaque white, soft (H.=2), 
possesses a dull pearly luster, and has a fibrous to columnar 
structure. Small grains are found disseminated through the 
ore, but it usually appears in the fissures, when it forms the 
matrix for rounded crystals of chondrodite and magnetite and 
crystals of chlorite. ‘The chlorite and serpentine occur i all 
} . 
from bright green to pure white, and in texture from the folia- 
Am. Jour. Sc1.—Turp Serres, Vou. VI, No. 33.—SEPT., 1873. 
14 
