Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-11-16

THE most abundant Of all minerals is prob
ably one about which the general run Of
people have the least knowledge. The mineral
in question, feldspar, despite its lack Of ac-
quaintance with the general public, Is widely
used, being an essential Of the glass, brick,
pottery, enamelware, bathtub, securing soap.
paint and false teeth industries
Feldspar is not the name Of q specific min
eral. 1t Is a general term in mineralogy for
an important group Of rock-forming minerals
consisting Of several species, all Of them
anhydrous silicates Of aluminium containing
either potash, soda or lime, or two OF these
bases together. These varieties are divided into
two groups, the potash feldspars and the lime
soda feldspars. Orthoclase and microcline are
the chief representatives Of the hrst group,
while albite and oligoclase are the most inn
portant Of the second or plagioclase group.
Orthoclase and microcline are the most inn
portant feldspars Of commerce and are Of COM
mon occurrence.
Feldspar occurs abundantly In granite but
the difnculty of separating it from the inn
purities associated with it is 50 great that such
occurrences under present conditions must re-
main unutized and commercial supplies must
be sought in those restricted occurrences where
nature has made desired separation. The field
spar Of commerce Is obtained from pegmatite
bikes.
The principal use of feldspar is as o flux
in the manufacture Of glass, pottery, enamel
ware, brick and tile. It is q constituent Of
both body and glaze Feldspar, which constitutes
from 10 to IS per cent OF the body, Is used to
bind the particles together. The amount Of
feldspar used IN the glaze ranges from 80 TO
so per cent. Various forms Of Opaque glass that
md use IN hotels, restaurants drug stores and
other places where q vitrefed surface is de-
sired for sanitary reasons contain considerable
quantities of feldspar. Bath tubs and wash
bowls are commonly made of cast iron, and
while hot are covered with an enamel contain
ing much feldspar. It Is also an important
constituent of electrical and other forms Of
porcelain Exceptionally pure potash feldspar
Is used in the manufacture Of artificial teeth
The use of feldspar in the glass industry is
increasing, rs 1t provides readily soluble source
Of alumina. Potash feldspar is widely used,
though mixtures Of soda and potash spar are
also sold to glass manufacturers; IL Is also
employed with fiuorspar in the manufacture Of
opalescent glass. Feldspar provides both
alumina and the alkalies In the manufacture
Of bottle and pressed glass products.
Up to the present time feldspar has found
limited use in the window and plate glass in-
dustries, though some manufacturers are fnd-
ing it advantageous. It's general acceptance
would increase the demand for feldspar enor-
mously.
Very clean feldspar is used as a constituent
Of securing soaps and window cleaning COM
pOunuS. IL Is pIelSIIc0 70 QUARTZ aDraSlVeS Tor
cleaning glass and enamelware because it is
somewhat softer than quartz and is less likely
to scratch the surface. Pure feldspar is also
used as a binder In the manufacture of emery
and carborundum wheels.
The more impure grades Of feldspar find use
in the manufacture Of certain floor coverings
and as constituent of roofing material, sand
paper. paint, wood filler and terra Gotta Ground
feldspar Is also used as q fiue-dust arrester.
Crushed spar Is used in considerable quanti-
ties in the form Of granules for resurfacing pre-
pared roofing, IN concrete work, in stucco and
pebble DASH in Faience work, and in the facing
Of cement blocks particularly those designed
10 resemble granite. 1t Is used as sand-blast
material and as poultry grit Crushed ssAax
graded IN several sizes Is sold for foundry
facings.
Potash feldspar has at times been used IN
portland cement manufacture to increase the
potash yield where potash recovery was prao-
ticed. Ground feldspar Is Of Saime ms 8 1eR~
till3er only under exceptional CoAAEtions be-
eaa1se the potash % IA d form Zoe ansoldhle 1ow.