The beryllium tuff member of the Spor Mountain Formation contains abundant carbonate clasts southwest of Spor Mountain. Porous, reactive carbonate-clast tuff provides a suitable host for beryllium ore. Much tuff is incompletely mineralized: former dolomite clasts bleached white to calcite. The following examples, from the Monitor pit, illustrate the carbonate-clast facies of the beryllium tuff.
SLIDE 48 (black and white) shows tuff beds distinguished by varying amounts of carbonate clasts. Note pick in center of photo, on bed containing abundant carbonate clasts. Manganese oxide minerals follow and cut across bedding in the beryllium tuff. Some of the tuff is incompletely altered; although not analyzed, it is probably not ore.
SLIDE 49 shows a closeup view of incompletely mineralized carbonate clasts in tuff. Note bedding plane at pick in lower left; carbonate clasts are sparse in the the bed above the pick.