1911 Encyclopædia Britannica, Volume 18… (1911)
“ This Missouri tripoli is a finely decomposed light rock, about 98% silica, and is used for filter stones and as an abrasive. “Chat”—finely crushed flint and limestone yielded as tailings in the lead and zinc mines—finds many uses. Limestone is quarried all over the state (except in the embayment region) . There are unlimited supplies of clay, shale and limestone, the three essential constituents of Portland cement, and the manufacture of this, begun in 1902, at once assumed important proportions. Quicklime manufacture is also an important industry. ”
