At Baita Bihor (formerly Rézbánya), Romania, the type locality szaibelyite occurs in magnesian skarns hosted by the dolomitic marbles of Mesozoic age, near the contact with a granite - granodiorite body of Upper Cretaceous - Paleogene age. Associated minerals include calcite, dolomite, magnesite, kotoite, suanite, ludwigite, fluoborite, fluorite, chondrodite, norbergite, magn etite, brucite, chrysotile, lizardite, clinochlore, lepidocrocite and goethite. Szaibelyite from Baita Bihor is extremely close to the end- member composition (Mg2(B2O4OH)(OH)). Up to 0.88 mol.% sussexite (the Mn end-member), 1.06 mol.% Fe2(B2O4OH)(OH) and 0.20 mol.% Ca2(B2O4OH)(OH) may be deduced on the basis of combined wet-chemical and electron-microprobe analyses. The mineral exhibits very slight fluorine contents ( XF = F/(F + OH) ≤ 0.01). Selected-area electron imaging supported by X-ray powder patterns indicate that the szaibelyite from Baita Bihor is monoclinic, space group P21/a. The mean unit-cell parameters are a 12.559(18), b 10.402(12), c 3.132(8) Å and 95.77(33)°. Thermogravimetric curves gave a smooth and continuous weight- loss of up to 3.39 wt.% H2O between 150 and 600°C, in reasonable agreement with the results obtained by loss on ignition. The complete dehydration occurs between 650 and 700°C, the breakdown product being the monoclinic (P21/a) polymorph of Mg2(B2O5). Two OH-stretching bands in the infrared absorption spectra of the mineral, at ~3560 and ~2510 cm -1, respectively, are indicative of two distinct hydrogen positions in the structure. The IR spectra do not systematically show absorption system - atically at ~1630 cm-1 (bending mode of H2O), suggesting that the mineral does not contain molecular H 2O. Szaibelyite from Baita Bihor is estimated to have developed at temperatures of 160-450 °C, pressures of 0.6-3 kbar, at relatively high activity of fluorine, and at low potentials of iron and manganese.

A carbonate-bearing, fluorine-overcompensated fluorapatite (F = 4.42 wt.% as compared with 3.77 wt.% F in the Ca₅(PO₄)₃F end-member), was identified in forsterite-bearing skarns from Valea Rea (N 46°39′48″, E 22°36′43″), located near the contact of the granodiorite laccolith from Budureasa, of Upper Cretaceous Age, with Anisian dolostones. The chemical structural formula (with carbonate not included) is: (Ca_4.989Mn_0.001Fe²⁺_0.003Mg_0.003Ce_0.001La_0.001)(P_2.992Si_0.008)(O_11.894F_1.202Cl_0.001). No major structural distortions due to (CO₃F)^3--for-(PO₄)^3- replacement were identified by single crystal X-ray diffraction, Raman or FTIR. The mineral crystallizes in space group P6₃/m, having as cell parameters a = 9.3818(1) Å and c = 6.8872(1) Å. The indices of refraction are: ω = 1.634(2) and ε = 1.631(1). The calculated density is D_x = 3.199 g/cm³ and the measured density is D_m = 3.201(3) g/cm³. Calculation of the Gladstone–Dale compatibility indices gave in all cases values indicative of superior agreement between physical and chemical data. In the infrared spectra, the multiplicity of the bands assumed to phosphate modes (1ν₁ + 2ν₂ + 3ν₃ + 3ν₄) agrees with the reduction of the symmetry of PO₄³⁻ ion from T_d to C₆. Chemical peculiarities and textural relations agree with a hydrothermal origin of the mineral, crystallized from F-rich fluids originating from the granodiorite intrusion.

A shallow-level monzodioritic to quartz-monzodioritic pluton of the Upper Cretaceous age caused contact metamorphism of Tithonic–Kimmeridgian reef limestones at Măgureaua Vaţei (Metaliferi Massif, Apuseni Mountains, Romania). The preserved peak metamorphic assemblage includes gehlenite (Ak 33.64–38.13), monticellite, wollastonite-2M, Ti-poor calcic garnet, and Ca-Tschermak diopside (with up to 11.15 mol.% Ca-Tschermak molecule). From the monzodioritic body to the calcitic marble, the periplutonic zoning can be described as: monzodiorite/agpaitic syenite-like inner endoskarn/wollastonite + perovskite + Ti-poor grossular + Al-rich diopside/wollastonite + Ti-poor grossular + diopside + vesuvianite/gehlenite + wollastonite + Ti poor grossular + Ti-rich grossular (outer endoskarn)/wollastonite + vesuvianite + garnet (inner exoskarn)/wollastonite + Ti-rich garnet + vesuvianite + diopside (outer exoskarn)/calcitic marble. Three generations of Ca garnets could be identified, as follows: (1) Ti-poor grossular (Grs 53.51–81.03 mol.%) in equilibrium with gehlenite; (2) Ti-rich grossular (Grs 51.13–53.47 mol.%, with up to 19.97 mol.% morimotoite in solid solution); and (3) titanian andradite (Grs 32.70–45.85 mol.%), with up to 29.15 mol.% morimotoite in solid solution. An early hydrothermal stage produced retrogression of the peak paragenesis toward vesuvianite, hydroxylellestadite (or Si-substituted apatite), clinochlore, “hibschite” (H₄O₄-substituted grossular). A late hydrothermal event induced the formation of lizardite, chrysotile, dickite, thaumasite, okenite and tobermorite. A weathering paragenesis includes allophane, C-S-H gels and probably portlandite, unpreserved because of its transformation in aragonite then calcite. Overprints of these late events on the primary zoning are quite limited.

An ammonium-bearing fluorapophyllite-(K) occurs as a late hydrothermal product in the outer endoskarn zone from Aleului Valley (N 46°37′04″, E 22°35′22″), located at the contact of the granodiorite laccolith from Pietroasa, of Upper Cretaceous age, with Anisian dolostones. Associated minerals are wollastonite, K feldspar, diopside, fluorapatite, talc, and pectolite. The chemical structural formula is [K_0.985Na_0.012(NH₄)_0.076]_Σ=1.073(Ca_4.009Mn_0.001Fe²⁺_0.003Mg_0.002Ba_0.001)_Σ=4.016(Si_7.953Al_0.047) O_20.029[F_0.899(OH)_0.101]·8.059H₂O. The structure was successfully refined as tetragonal, space group P4/mnc, with cell parameters of a = 8.9685(1) Å and c = 15.7885(5) Å. The indices of refraction are ω = 1.534(1) and ε = 1.536(1). The calculated density is D_x = 2.381 g/cm³, in good agreement with the measured density, D_m = 2.379(4) g/cm³. The thermal analysis shows that the mineral completely dehydrates at up to 450 °C (endothermic effects at 330, 371, and 448 °C) and loses ammonium at 634 °C. In the infrared spectra, the multiplicity of the bands assumed to be silicate modes (1ν₁ + 3ν₃ + 2ν₂ + 3ν₄) agrees with the reduction in the symmetry of the SiO₄⁴⁻ ion from T_d to C_δ. Fluorapophyllite-(K) from Aleului Valley is of late hydrothermal origin and crystallized from F-rich fluids originating from the granodiorite intrusion, which mobilized K, Ca, and Si from the pre-existing feldspar.

This paper presents a new account of the mineralogy of the bat guano deposit in Gaura cu Muscă Cave, Locvei Mountains, Romania. The cave, which, in its main proportion, is a wet, “live” cave, has a dry portion hosting guano. Biogenic leucophosphite is one of the main compounds of the fossil bat guano association in the cave, where it occurs together with hydroxylapatite, taranakite, ardealite, calcite, quartz and illite (the 2M1 polytype). The mineral species from the cave were characterized by optical methods, scanning electron microscopy, wet-chemical analysis, X-ray powder diffraction, Fourier-transform infrared and inductively coupled plasma – atomic emission spectrometry. The crystal-chemical formula of leucophosphite from Gaura cu Muscă is [K_0.978Na_0.003(NH₄)_0.014](Al_0.085Fe_1.903Mg_0.001Mn_0.006)(PO₄)₂(OH)_0.973·2H₂O. The cell parameters calculated for the same sample are a = 9.813(6) Å, b = 9.749(6) Å, c = 9.631(9) Å and β = 102.30(2)°. The infrared spectrum affords the presence of (PO₄)³⁻, (HPO₄)²⁻, (NH₄)⁺ and (OH)⁻ ions, together with H₂O molecules. The band multiplicity on the IR absorption spectrum suggests that the phosphate groups in the structure have C_s punctual symmetry. The host deposit was formed under extremely “dry” conditions that favored a sharp decrease in the pH of solutions derived from the guano mass.