206 NEW YORK STATE MUSEUM 
from the latter in the hand specimens. Its occurrence-may account 
for the high aluminum percentages shown in analyses of the mag- 
netites, even in the absence of corundum. The latter is a fluctuating 
constituent, constituting as much as 50 per cent. of the emery in 
places, but usually considerably less. It appears in the form of 
thin prismatic crystals which are set off by reason of their light 
color and their relatively large size from the magnetite and spinel. 
The mines consist of open cuts on the outcrop of the bodies, 
occasionally supplemented by a single underground level reached 
through an adit. They have little permanent equipment, being too 
small to warrant any considerable outlay for machinery; conse- 
quently there is a lack of stability and system to the operations. 
The present source of supply is mainly from one or two proper- 
ties on the northern border of the Cortlandt area. The Keystone 
Emery Mills and the Blue Corundum Mining Co. have been the 
principal shippers of recent years. There are a number of mines 
in the section north of Dickinson hill and south of the east-west 
highway leading out of Peekskill, but most have been closed either 
on account of exhaustion or the unsuitable character of the material. 
Some of the more extensive workings are on the farms of John 
Buckbee and Oscar Dalton. 
FELDSPAR 
Feldspar is one of the minor products for which the market in 
this section hitherto has been rather limited. The pottery trade 
in which the better or more valuable grades find use has only 
recently come into prominence in New York, and the larger centers 
without the State, as those of Ohio, West Virginia and New Jersey, 
can usually be supplied more cheaply from other sources. Thus 
the principal quarries of pottery spar are found in New England, 
the Southern States and Canada. The local quarries in the Adiron- 
dacks and the southeastern metamorphic belt have never been able 
to compete very successfully in this branch of the business. 
With the recent growth of the pottery business, now represented 
in many branches and in various parts of the State, there would 
seem to be opportunity for development of some of these resources 
to meet the requirements of the local market. 
The uses of feldspar, aside from that of pottery manufacture, 
are sufficiently varied to afford a basis for regular quarry opera- 
tions such as are carried on at present. One of the principal ap- 
plications is in the preparation of roofing material, where it is 
