Variscite (AlPO₄ 2H₂O) from Cioclovina Cave (Sureanu Mountains, Romania): a tale of a missing phosphate

Authors

Bogdan P. Onac, Department of Mineralogy, "Babeş-Bolyai” University & “Emil Racoviţă” Institute of SpeleologyFollow
Joe Kearns, Materials Research Institute, The Pennsylvania State University
Radu Breban, S.C. Roşia Montană Gold Corporation S. A.
Simona Cîntă Pânzaru, Department of Molecular Spectroscopy, "Babeş-Bolyai” University

Abstract

Recent investigations on a phosphatized sediment sequence in the Cioclovina Cave led to the identification of a second occurrence in Romania (first time in the cave environment) of variscite, AlPO4·2H2O. The mineral exists as dull-white, tiny crusts and veinlets within the thick argillaceous material accumulated on the cave floor. Under scanning electron microscope (SEM) variscite appears as subhedral to euhedral micron-size crystals. The {111} pseudo-octahedral form is rather common. Variscite was further characterized by means of X-ray diffraction, thermal, vibrational FT-IR and FT-Raman spectroscopy, and by SEM energy-dispersive spectrometry (EDS). The calculated orthorhombic cell parameters are a = 9.823(4), b = 8.562(9), c = 9.620(5) Å, and V = 809.167(6) Å3. The ED spectrum of variscite shows well-resolved Al and P lines confirming thus the presence of the major elements in our compound. The formation of variscite is attributed to the reaction between the phosphate-rich leachates derived from guano and the underlying clay sediments.

Recommended Citation

Onac, Bogdan P.; Kearns, Joe; Breban, Radu; and Cîntă Pânzaru, Simona (2004) Variscite (AlPO₄ 2H₂O) from Cioclovina Cave (Sureanu Mountains, Romania): a tale of a missing phosphate, Studia UBB Geologia 49 (1): 3-14
DOI: http://dx.doi.org/10.5038/1937-8602.49.1.1
Available at: https://digitalcommons.usf.edu/geologia/vol49/iss1/art1