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

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