356 TJic American Geologist. December, i9oo 
Tremolite occurs in the fibrous form, partially surrounded 
by fayalite. 
Its birefringence is at least .024. The elongation of the 
fibers is always positive, with a maximum extinction angle ot 
about 16° 
Actinohte is simply a ferriferous tremolite, and differ? 
from the latter only in its pale green color, distinct pleochro- 
ism, and slightly smaller maximum extinction angle. It 
seems to be derived from the tremolite by the addition of iron, 
and is undoubtedly always secondary. Its pleochroic colors 
/% = clear green 
«m = greenish ? yellow 
;/p = pale yellow 
The maximum extinction angle parallel to the elongation 
does not exceed 13°. 
Boivlingite is the ordinary decomposition product of the 
fayalite. It occurs very sparingly, and is usually of lamellar 
habit. The color is quite variable, reddish yellow, brown, 
or green. The pleochroism is remarkably w-eak. 
Got/lite is another more uncommon alteration product of 
fayalite, and can be distinguished from the reddish yellow 
bowlingite only by the fact that it has a higher refringence 
than the fayalite, while bowlingite has a lower. It has a red 
color, and a birefringence superior to .012. The lamellae, ap- 
parently homogeneous, are found to be composed of many 
parts of varying orientation; this fact, together with a very 
strong dispersion, prevents extinction in white light. 
Hematite occurs merely as a superficial rusty stain; it has 
not been found in sections of the rock. It is doubtless formed 
by oxidation of the magnetite. 
Penninite and cli)wclilore have only been observed along 
fractures in the rock. 
The CHEMICAL COMPOSITION of the silicoferrolyte is char- 
acterized by the high per cent of iron and extremely low silica. 
Titanium occurs in very small amount. This is the more sur- 
prising since the gabbros are so commonly titaniferous in this 
region. The very low per cent of alkalies is another notable 
feature. The per cent of water is surprisingly high. 
