Unusual Minerals Related to Phosphate Deposits in Cioclovina Cave, Şureanu Mts. (Romania)

Cioclovina Cave hosted an extensive phosphate deposit estimated at over 50,000 m3. About 30,000 m3 were mined during the first half of the XXth Century and used as fertilizers. The mineralogy of this deposit is remarkable as it consists of several rare and/or unusual cave mineral species, mostly phosphates. Cioclovina Cave is the type locality for ardealite. Over 40 samples were analyzed by means of X-ray diffraction and fluorescence, scanning electron microscopy, optical observations on thin sections, and electron microprobe. Out of 26 minerals presented in this paper, 13 have not been previously documented from this cave (berlinite, burbankite, churchite, chlorellestadite, foggite, paratacamite, collinsite, monetite, fluorapatite, sampleite, romanechite, leucophosphite and todorokite). Furthermore, the first six minerals on this list were for the first time identified within the cave environment. At least one rare mineral species (berlinite or chlorellestadite) may have been produced by spontaneous combustion of bat guano, whereas the other ones formed within the sediment fill indicate reactions between phosphate-rich solutions and limestone bedrock, clays, sandstones or various trace elements. These reactions took place at different pH values producing specific minerals that may have environmental deposition significance