i 
220 T. S. Hunt on Ophiolites. 
magnesia. This serpentine contains a small quantity of chromic 
iron. The oxyd of nickel, determined upon four grams of the 
mineral, gave no trace of cobalt before the blowpipe. Its analy- 
sis gave as follows :— 
Silica, - . - - - . 42°90 
= - - - - 36°28 
Protoxyd of iron, - - - 2 i TAT 
Oxyd of nickel, - - - = : mn 15 
Chromic iron, - ped . F 35 “25 
Loss by ignition, - - - - - 1314 
100719 
3. I may cite in this place the analysis of a serpentine given 
in my Report for 1852, p. 99. It forms the rock in contact with 
of chromic iron ore in Ham, has a hardness of 3°5, and 
a density of 2:546. It is massive and compact, with a splintery 
acture; color greenish-white, and translucent. The analysis, 
which failed to detect either chrome or lime, gave as follows:— 
Silica, - - “ . 43-4 
Magnesia (by difference), - - - - 400 
Alumina and oxyd of iron, - - : - 36 
Water, - - - “ - . -"..180 
100°0 
Silica, r i m E 43°70 
Magnesia, - - . - - - 40°68 
Protoxyd of iron, — - : 2 . - 3°51 
Oxyd of nickel (undetermined). - = 
ter, - ‘ F 12°45 
100°34 
5. Caleareous Ophiolite—The specimen of this variety whicl 
I have analyzed is from the saath lot of the sixteenth range ° 
Orford. It is fine grained and sub-crystalline, with @ scaly, 
somewhat conchoidal fracture. Color, mottled greenish-gt)+ 
