The Eocene Mt. Laird Tuff, named for the type locality at Mt. Laird (near Joy townsite in the Drum Mountains) contains widely varying facies, including crystal-rich latitic ashflow tuff and tuffaceous lakebeds in the subsurface east of Topaz Mountain, and crystal-rich tuff or flow rock and breccia near Mt. Laird. The thickest, and most complete, section lies in the subsurface; for details, see Lindsey (1982). All facies share abundant plagioclase and hornblende crystals and a distinctive grayish pink color.

SLIDE 19 shows a typical breccia mapped within the Mt. Laird Tuff in the type locality. Breccia clasts are vesicular and set in a matrix of Mt. Laird Tuff. Unquestioned pumice and shards were not identified, casting some doubt on whether the breccia is actually tuff or a flow breccia. If tuff breccia, it could represent a vent area for the Mt. Laird Tuff.