the Tilly Foster Iron Mines. 211 
One other variety of this species deserves a passing mention ; 
it is massive, of an olive-green color, with a porcelain-like luster 
on the smooth fractured surface. No analysis was made 
Amphiboles.—Several varieties of the amphibole group of 
bisilicates appear at this locality, and are quite abundant, oc- 
curing usually along the walls of the ore bed. Of two varieties 
ave made analyses. 
Enstatite—This occurs massive, having a slight fibrous ap- 
pearance with a pearly to vitreous luster on a broken surface, 
and is of a light grayish-brown color, with a yellow tinge by 
transmitted light. In thin pieces it is translucent. It is quite 
ee from impurities. There is no distinct cleavage. H.=5°. 
Infusible. Sp. gr. 8-29. The results given by analyses are— 
i Il. In. Mean. Oxygen. 
SiO, 416 8419. eee 
Al,O, 3°35 S85 ce 3°3 1°40 
FeO 9°90 a ce eee 9°94 2°19 
MnO 24 ah ee 24 : 
MgO Soe STF 31:99 12% 
CaO 1-01 : tee 99 28 
K,0 oie fee 16 IGS. 
a,O i&e aA “32 32 ner 
ation os Plame 13 13 ets 
101-24 
Oxygen ratio for &, $i, 16:29, approximately the Mg Si of 
enstatite ; the composition shows it to be this mineral. If the 
5 a an considered as replacing SiO,, we have a ratio of 
Actinolite—This variety of hornblende occurs in consider- 
able abundance, and is generally crystalline, often only ob- 
securely so. A few fine crystals were found. The erystallized 
d 
Widely disseminated through the specimens examined, even in 
fine crystals, that it was with great difficulty enough was ob- 
tained to make an analysis. The results obtained are— 
IIL. 
I. I. Oxygen. 
SiO, 8750. 3750" © 5744 29°61 
Al,O, 113 4 Sa 11 52 
FeO 4°36 430 2026: 4°33 85 
MnO 15 16 Eas 15 
CaO 13°22 13°36 Boi 13°29 3°83 
MgO 29°56 40«-22°63——t—i‘ | 22°59 8°92 
K,0 ceo ee etaon tr. ---- wees 
Na,O ae ea tr. ; adas 
H,O me oe 1°52 1°52 1°34 
