ORES OF MANGANESE AND CHROMIUM 131 
with so many veins of chromite that it has a stratified aspect. 
The adjacent serpentine is intensely broken and slicken- 
sided. The ore band yields about 7 per cent. of chromic 
oxide, but nodular expansions of the veins contain 50 per 
cent. Some veins of an acid rock with vesuvianite project 
from the ore into the serpentine. The ore was formed 
after the consolidation of the peridotite of which the ser- 
pentine is the altered representative, and the chromite veins 
were deposited in a band crushed by earth-movements! 
(Cirkel, Chrome Irom Ore, Quebec; Canada Dep. Mines, 
1909). 
Chromite occurs in Beluchistan, Mysore, etc., also in ser- 
pentine in veins which are presumably later than the rock. 
In California, at Little Castle Creek, the chrome ore is in a 
serpentine formed from pyroxenite; the lower part of the 
rock is too poor to be mined, and the ore is just below the 
outcrop, as if concentrated by secondary enrichment. 
As chromite is a primary constituent of basic rocks, its 
ores have been often regarded as igneous segregations. This 
origin appears probable for some cases. Thus in the gneiss of 
Maryland an intrusive peridotite, which contains no chromite 
but -5 per cent. of chromic oxide, is surrounded by an irregular 
sheath of chromite which is attributed to its concentration in 
the quickly cooled margin of the magma (Pratt and Lewis, 
N. Carolina G.S., i, 1905, pp. 370, 372). Nevertheless the 
ores of most economic importance, whatever may have been 
the original source of their chromite, are secondary ; _they 
are found in veins and nodules that were formed after the 
country had been altered to serpentine, and even after that 
rock had been fractured. The slicken-siding of the lenses 
and masses of ore shows their association with earth-move- 
ments, which by crushing the rock rendered possible the con- 
lentration of its scattered grains of chromite. 
The price of chromium ore is based on the percentage of 
chromic oxide (Cr,0,). Ore shipped from Southern Rho- 
desia containing 52 to 54 per cent. has been sold at the port 
of shipment since 1914 at from 43s. to 89s. per ton; poorer 
ore is used as a refractory material for lining furnaces for 
smelting iron. 
! Dresser considers that the dislocations were later than the segre- 
gation of the chromite though recognizing the vesuvianite as pneuma- 
tolytic (G.S. Canada, Mem. 22, 1913, Pp. 74-95).