14 CORUNDUM IN THE UNITED STATES. bull. 180. 
one another; c represents a narrow zone of vermiculites that is some- 
times entirely lacking; r/, a green chlorite (clinochlore) partially 
decomposed and forming the vermiculites of c; e, the corundum- 
bearing zone, a mass of the green chlorite with crystals and frag- 
ments of corundum disseminated through it; /, another zone of the 
green chlorite; g, a mass of grayish, interlocking, crystalline sheaves 
of enstatite that merge into In; h, a fibrous talcose rock which passes 
into j; j, an altered dunite that is somewhat friable and stained with 
ferric oxide; k, a hard and apparently unaltered dunite. Between h 
and j is a mass of soft, yellowish clay (/) containing fragments of 
chalcedony. 
The line of contact between the zone of alteration products and the 
gneiss was very sharp and distinct in all the contact veins examined. 
The minerals developed between the corundum-bearing zone and the 
dunite are in great abundance and differ from those between that 
zone and the gneiss. 
In a cross section of a dunite vein at a shaft near the southern part 
of Corundum Hill, in a distance of from 20 to 25 feet, the following 
has been observed: 
1. Dunite, hard and apparently unaltered. 
2. Dunite, somewhat friable and discolored, passing into 3. 
3. Talcose rock, fibrous, merging into 4. 
4. Enstatite, grayish and somewhat fibrous. 
5. Green chlorite, 6 to 15 inches in width. 
6. Green chlorite, corundum, and spinel, G to 8 feet wide. 
7. Chlorite, same as 5. 
8. Enstatite, same as 4. 
9. Talcose rock, same as 3. 
10. Dunite. same as 2. 
11. Dunite, same as 1. 
The similarity of the two parts of the vein separated by the corun- 
dum zone, as already described and as illustrated in fig. 2, is very 
apparent. 
In fig. 2, 1 and 11 represent the apparently unaltered dunite; 2 and 
10 represent dunite somewhat friable and stained and passing into 
3 and — a fibrous talcose rock, often carrying a green actinolite and 
some green chlorite; 4 and 8 represent a grayish, rather fibrous ensta- 
tite rock, which merges into 3 and 9; 5 and 7 represent a green chlorite, 
which passes into — a mass of chlorite, corundum, and spinel. 
Although the section just described is a special case, it was observed 
that all of the dunite veins had the same character on both sides of 
the corundum-bearing zone. As has been already stated, either a 
talcose or a serpentine rock may be the limit of the cross section. 
In one of the dunite veins at Corundum Hill near the west end of the 
outcrop, the zone of corundum, chlorite, and vermiculites is in direct 
contact, both on the hanging and on the foot wall, with a serpentine 
rock. This zone is divided — in one place almost pinched out — by a 
mass of serpentine. 
