PRATT. ! 
MODKS OF (Kri'KKHNCK. 
23 
exploration for corundum, which, according to Lewis, 1 was found to 
occur in fine brown vermiculite, developed in zones along the borders 
of and penetrating the amphibolite, and varying in thickness from a 
few inches to 3 or 4 feet. Fig. 6 is an ideal illustration of the occur- 
rence of corundum in the amphibolite at Hunters. In this figure, a 
represents a feldspar vein thai is sometimes encountered in the midst 
of the vermiculites, b; the feldspar is more or less altered to kaolin, 
and often bears eoriindniii. although most of it was found in the 
vermiculite zones, b represents the vermiculite zones carrying the 
corundum, which is in crystals and in rounded masses of crystals clus- 
tered together. Margarite soniei Lmes accompanies it, and Large masses 
made up almost entirely of these two minerals have been found on 
the surface in this region, c represents radiating borders of actinolite 
that inclose large masses of what was once amphibolite, but which 
- - / -, 
mpyc 
PlQ.tt.— Ideal vertical cross section of corundum in amphibolite at Hunters, Iredell County.N 
is now uothingbul a mass of ocherous clay, bearing occasional needles 
of hornblende and scales of vermiculite. The outer portions, J, are 
dark -green amphibolite. 
CORUNDUM (EMERY) IN AMPHIBOLITE AT CHESTER, MASS. 
The most widely known occurrence of corundum in amphibolite is 
that of the emery at Chester, Mass., an elaborate description of which 
is given by Prof. I J. K. Emerson 1 in his exhaustive work on the geol- 
ogy of old Hampshire County, Mass. 
Extending almost continuously across the State, north and south of 
Chester, there is a band of amphibolite that is conformable through- 
out its entire extent with the sericitic schists of this section of the 
Mon. U. S. Geol. Survey Vol. XXIX, 1898. 
