Fire Clay Pit (MRDS - 10147337), Gerald, Franklin County, Missouri, USAi

Regional Level Types
Fire Clay Pit (MRDS - 10147337)	Pit
Gerald	Village
Franklin County	County
Missouri	State
USA	Country

METATORBERNITE IN MISSOURI FLINT FIRE CLAY
BY OLIVER R. GRAWE

In 1940 J. G. Grohskopf of the Missouri Geological Survey obtained from Mr. Edward Sassman, Mining Superintendent, The General Refractories Company, Owensville, Missouri, a specimen of flint fire clay, on the surface of which, were tiny green scales of a mineral not previously observed in the fire clays of Missouri. The specimen was identified by the writer as metatorbernite, a hydrated copper uranyl phosphate, Cu (U02) 2 (P04)2·8 H20, and on March 22, 1941 he visited the pit from which the mineral was obtained. This pit is one of the typical sink structures common to central Missouri. It is on land owned by Eliza Gelauf in the NW1/4 SW1/4 SW1/4 sec. 32, T. 42 N., R. 3 W., about 5 1/2 miles southeast of Gerald, Franklin County. The mineral occurs as very thin apple green plates, square or octagonal in outline, and about one to two millimeters on edge. The plates are soft, have a distinct pearly luster, and a refractive index of 1.626 in the square section. They yielded distinct tests for copper, uranium, and the phosphate ion, and distinctly fogged a photographic film on which they were placed, indicating their radioactivity. The mineral was observed to occur chiefly on spheroidal masses of bad clay, so-called "sore spots" about 20 feet beneath the surface, and was associated with barite, a small amount of chalcopyrite, and limonite. It undoubtedly is secondary and is chiefly of interest because of its radioactivity. A determination of the age of this mineral might throw some light on the time at which some mineralization took place in Missouri. So far as the writer is aware, this is the first radioactive mineral to be described from the State.