Joe Kearns

Revisiting three minerals from Cioclovina Cave (Romania)

The investigated area is in the Grădiştea Muncelului-Cioclovina Natural Park, located in the western part of the şureanu Mountains (also known as Sebeş Mts.), a major unit of the Transylvanian Alps (Martonne, 1907; Fig. 1a). Cioclovina Cave is a world-renowned site for its paleontological (Simionescu, 1941; Breban et al., 2003), anthropological (Olariu et al., 2002; Soficaru et al., 2007; Alexandrescu et al., 2010), and mineralogical (Onac et al., 2002, 2007; Onac & Effenberger, 2007; Dumitraş, 2008; Onac & Tămaş, 2010) finds, being declared a scientific reserve since 1979. The cave represents the type locality of ardealite (Schadler, 1932). From a total of 1,400 m of surveyed passages (Tomuş, 1999;

VARISCITE (AlPO4·2H2O) FROM CIOCLOVINA CAVE (ŞUREANU MOUNTAINS, ROMANIA): A TALE OF A MISSING PHOSPHATE

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) A, and V = 809.167(6) A 3 . 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.

Secondary sulfates found in an old adit from Rosia Montana, Romania

5 ABSTRACT. Recent investigation on several secondary minerals formed in old mining galleries in the Cârnic district (Rosia Montană, Romania) enabled us to characterize ten minerals. Out of these ten identified minerals, the discovery of jokokuite is the first reported occurrence in the Carpathians. A second mineral identified as apjohnite represents a new occurrence in Romania. Along with these two rare minerals, some other species of the halotrichite group (pickeringite, halotrichite, apjohnite, and dietrichite), iron sulfates, and K-Al sulfates were identified. Minerals were identified using light microscopy, X-ray diffraction, infrared, and scanning electron microscopy with energy dispersive spectroscopy. The chemical composition of some samples was determined with inductively coupled plasma atomic emission spectrometry. The precipitation of these sulfates is largely controlled by cations substitutions and changes in the temperature, relative humidity, and evaporation along the sampled gallery. The general sequence of sulfate deposition at the investigated site includes the following main steps: (1) oxidation of pyrite by meteoric water seepage through dacites to create ferrous sulfate and sulfuric acid solutions; (2) chemical reaction between dacites and sulfuric acid from which other cations (Al 3+ , Zn 2+ , Mn 2+ , K + ) are released into solution; and (3) precipitation of various hydrated sulfates as a result of a combination of dehydration/hydration, oxidation, and neutralization reactions that take place under different microclimatic settings.