THE MINING AND QUARRY INDUSTRY I9Q12 27 
employed as a surface coating with tar or some bituminous binder. 
The spar is crushed to pea size or a little coarser and by reason of 
its good cleavage yields flat surfaces that are of advantage in secur- 
ing firm adherence. The purity of the material, however, is.a 
subordinate factor; the pegmatite which contains more or less 
quartz, mica and other minerals, is crushed down to size just as 
it comes from the quarry. Besides the roofing grades, there is 
more or less fine material resulting from the crushing, which is 
sold for use in concrete and grout. A small quantity of the spar 
of the coarser size is sold for poultry grit. Crushed pegmatite for 
these purposes brings a low price, usually around $3 a ton. 
The quarries and mills making roofing spar are situated in the 
Adirondack region, and include those of the Crown Point Spar Co. 
at Crown Point and the Barrett Manufacturing Co. at Ticonderoga. 
The methods of milling are simple, being based on a system of 
gradual reduction and sizing by screens. For the first step, a coarse 
crusher of the Blake type may be used, followed by rolls. At the 
mill of the Crown Point Spar Co., a higher grade of spar that is 
sold to enamel ware manufacturers is made by crushing to fine 
size in a chaser. The spar is first sent to the Blake machine, is 
then dried and instead of passing through the rolls, goes to the 
chaser. 
Manufacturers of enamel ware, glazed brick and terra cotta 
consume considerable quantities of feldspar. The requirements 
for these purposes are more exacting than for ordinary roofing spar 
in that the material must be fairly free of iron or iron-bearing 
minerals and have a relatively low point of fusibility. The feldspar 
should also be fairly free of admixture with quartz, as the presence 
of the latter tends to raise the melting point. As soda feldspar or 
albite fuses at a slightly lower temperature than the potash varieties 
orthoclase and microcline, it has preference among the glazed brick 
and terra cotta manufacturers. The spar is prepared by fine grind- 
ing by a chaser or a pebble or ball mill, the operations in a pebble 
mill lasting about 5 hours and reducing the product to a size that 
over 90 per cent will pass a too-mesh screen. The glaze is added 
to terra cotta by dipping or SpayS with the prepared slip and 
then burning in a kiln. 
Another use for the local product is in the manufacture of 
opalescent glass. This requires a spar of about the same quahty as 
that for enamel ware, but may contain more quartz. The material 
is also ground to about the same size. 
