Open-file Report 232 - New Mexico Bureau of Geology & Mineral ...

temperature range the material expands. Pumice and scoria are
already naturally expanded due to lava vesiculation; procnssing
involves simply milling and sizing to specified grades.
Specialty uses of the lightweight aggregates often grow olt of
their utility in building construction products. Perlite, for
example, is used for cryogenic insulating in much the Sam,? way
is used as a residential building insulator.
Geologically, the lightweight aggregates are diverse, being
derived from sedimentary, volcanic, and intrusive igneous rock
types. Perlite, pumice, pumicite, scoria, and cinders a m found
in both lava flows and pyroclastic deposits. Expansible shale
occurs as special regions within shale strata. Vermiculite a is
secondary mineral produced when deep-forming plutonic rock
becomes exposed and altered. No indication of occurrence of
either vermiculite or perlite in San Juan County is found in
literature.
Specific descriptions of each lightweight aggregate follow
with use, geology, and potential discussed under each mintzral.
Generalizations about development potential can be made o-ler the
whole county for all lightweight aggregates. These minerals are
low unit-cost and for most applications have easily available
substitutes. If development cost of one becomes much higher than
the costs of the others, another will be used in place.
Development potential is thus dependent on prices of the other
aggregates. Transportation costs must be kept low, so
development potential is highly dependent on nearness to end use
centers. Prices in 1983 in New Mexico were as follows: p(zr1ite
$34/short ton and scoria, $6/ton (NMEMD, 1984, p. 109, 111). The
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