New Mexico Bureau of Mines & Mineral Resources Bulletin 117 Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas

Phosphate and silicate minerals also occur in the caves of the Guadalupe Mountains, but these are rare compared to carbonate and sulfate minerals in the caves.

Phosphates

Where phosphate minerals do occur in Guadalupe caves, they are derived from bat guano. Fleischer (1951) reported "collophanite" (a collective name for a hydrous calcium phosphate) as a brown coating on a stalactite in Carlsbad Cavern, which he believed had formed by the reaction of calcium carbonate with bat guano. Hill et al. (1972a) reported fluorapatite, Ca₅(PO₄)₃F, as a blue-green layer in bat guano in a mined section of New Cave. On the basis of an optical analysis, Hill et al. (1972a) reported brushite, CaHPO₄·2H₂O, in Ogle Cave, but a later analysis of this material by x-ray diffraction showed it to be gypsum, the isomorph of brushite.

Silicates

Silicate minerals in Guadalupe caves are discussed in the speleogenesis section of this paper and will not be repeated here. They include: endellite (Pl. 6B), montmorillonite (Pl. 6A), and palygorskite (attapulgite). The endellite is believed to have derived from montmorillonite in the presence of low-pH, sulfuric-acid solutions. The attapulgite may have derived from montmorillonite when the clay was exposed to air.