Beryllium-bearing tuff in the Thomas Range, Juab County, Utah

Recently discovered beryllium deposits in the Thomas Range, Utah, are along the periphery of the fluorspar district at Spor Mountain. The beryllium is in altered rhyolite tuff of Tertiary age and is associated with genetically related fluorite, quartz, chalcedony, opal, calcite, and mont-morillonite and with residual quartz, feldspar, and biotite. Nodules of silica and fluorite contain more beryllium than the enclosing tuff. The ores probably were formed by fluorine-rich solutions derived from rhyo-litic magma related to a second period of volcanic activity.The district promises to be an important source of beryllium.