Brushite occurs as nodular masses of platy crystals in the lower part of a bat guano and hair deposit in Pig Hole Cave, Giles County, Virginia. Taranakite occurs as flour-like masses near contacts between the guano and hair deposit and clay and along fractures within brecciated clay within the same cave. Chemical, physical, optical, x-ray, and thermal data for each of these minerals are presented. Some of the thermal data for brushite and many of the data for taranakite are reported here for the first time. It is suggested that the taranakite formed as the result of reactions between the bat guano and bat hair and clay.