Heavy Minerals in the Wellborn Formation, Lee and Burleson Counties, Texas
At five places along the outcrop of the Wellborn Formation in Lee and Burleson counties, Texas, anomalously high gamma radiation is associated with concentrations of heavy minerals. The most abundant heavy minerals are ilmenite, magnetite, and zircon. The radiation is emitted by some radioactive element in zircon. The intensity of the radiation and the areal extent of the radiation anomalies were measured by a scintillation counter. The Wellborn Formation, composed of sediments deposited in near-shore environments, is characterized by cross-bedded sandstone lentils interbedded with montmorillonitic, lignitic shale and lignite. Heavy minerals in the lower part of the Wellborn are concentrated in thin sheets andwedges along cross-beds and in local patches and streaks. There are about 4 million tons of heavy mineral-bearing sandstone with an average of about 2 percent heavy minerals, or 2-1/2 million tons with an average of almost 3 percent heavy minerals. Locally, ilmenite, magnetite, and zircon make up as much as 25 percent of the sandstone, although concentrations are too small to be considered as commercial deposits under present  economic conditions.
Shelby, C. A., 1965, Heavy Minerals in the Wellborn Formation, Lee and Burleson Counties, Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 55, 54 p.
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The University of Texas at Austin, Bureau of Economic Geology
Report of Investigation