Diaspore clay is a harsh, usually porous, earthy type of clay which has
been found in Warren, Osage, Gasconade, Maries, Franklin, Phelps, and
Crawford counties in Missouri. Some diaspore clay is mealy, or finely
granular, some is chalky to compact, and much of it is more or less
oolitic. Oolites (oolitic structure) are small rounded bodies varying in
size from about bird shot to BB shot size, and those in diaspore may be
solid or hollow. Their hollow structure contributes to the porous
condition in diaspore clay. See page 29.
It is almost impossible to write a description of diaspore clay which
can be used to determine it because the clay has so few individual
characteristics. A person familiar with diaspore clay, however, can
recognize it at a glance. Probably diaspore clay will not be found
outside the counties listed above, and within those counties many
persons know the clay from contact with the commercial production of it.
[Illustration: Diaspore clay, over 70% alumina, from near Belle.]
Diaspore clay occurs in old sink-hole, funnel-shaped pits which formed
in the dolomite (limestone) underlying that region. A sandstone layer
which lines the pit and commonly stands somewhat above the level of the
clay because of the sandstones superior resistance to weathering is
known as the “rim rock” of the pit. The diaspore clay may be thought of
as an extra-refined type of fire clay from which silica has been leached
during prolonged solution in swamps and ground water and the more stable
alumina (Al₂O₃) left behind as the refined product.
Pits in the diaspore region may contain from a few truck loads of clay
to over 50,000 tons of it, but a pit which produces 10,000 tons of good
clay is a valuable and not very common deposit. A small fortune falls to
the landowner who finds a large diaspore deposit (pit) on his farm, for
royalty rates at this time are not less than $1.00 per ton for first
grade, 70% Al₂O₃ clay.
Because of the high value of diaspore, a highly competitive prospecting,
leasing, mining, and brokerage business has developed in the diaspore
region. Practically all of the thrills, hopes, disappointments, and good
fortunes that are associated with oil booms are found in this business
and clay area; clay pits are only smaller in scale than wild oil
gushers. Clay scouts work in secret, mining leases are contested in
court, rumors fly fast in English, German, and German-Swiss over the
country telephones, prospecting results may be hidden, personal pressure
may be brought to influence a deal, and speedy salesmanship is employed
when an exciting find is in the offing. When the legends, traditions,
and facts of the diaspore region are collected and recorded, an
interesting and essential part of Missouri history will have been
written.
Missouri has the only locality in the entire world where relatively pure
diaspore clay is now mined in commercial quantities. Because of its
extreme resistance to fusion under very high temperatures, diaspore has
been called the “aristocrat of fire clays.” Diaspore contains a higher
percentage of aluminum than does bauxite, the chief ore of aluminum, but
because of diaspore’s extremely refractory nature it is less easily
reduced to aluminum metal than is bauxite, and therefore finds a more
specialized use in the manufacture of refractory and super-refractory
brick and tile which may even be used in furnaces to calcine aluminum
ore. Where resistance to very high temperature has been required,
diaspore super fire brick has been remarkably useful.