Đorđević et al. (2016) noted 17 minerals and 12 synthetic compounds with the descloizite–adelite structure topology and provided the general formula M11+,2+M2^2+,3+(OH,O)[X4+,5+,6+(O₄,O₃OH)], where M1 = Na⁺, Ca²⁺, Cd²⁺, Hg²⁺, Pb²⁺; M2 = Mg²⁺, Al³⁺, Mn^2+,3+, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺; and X = Si⁴⁺, P⁵⁺, V⁵⁺, As⁵⁺, Mo⁶⁺. Among the minerals are eight arsenates, seven vanadates, and two silicates. One of the vanadates, gottlobite, CaMg(VO₄)(OH), has only been found at the Glücksstern mine, Gottlob Hill, Thuringia, Germany. In examining apparent gottlobite crystals from the Glücksstern mine, we found them to be the Pb analogue of the mineral, with the ideal formula PbMg(VO₄)(OH).

The new mineral is named plumbogottlobite based on it being the Pb analogue of gottlobite (Witzke et al., 2000). Note that we chose this name rather than magnesiodescloizite because the mineral is virtually identical in appearance to gottlobite and occurs in the same general mineral assemblage at the Glücksstern mine. The mineral and its name have been approved by the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC), proposal IMA2025-075 (Warr symbol: Pgot). The holotype specimen is deposited in the collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA, catalogue number 77403.

Plumbogottlobite was found on the dumps of the Glücksstern mine, Gottlob Hill, Friedrichroda, Gotha District, Thuringia, Germany (50°51^′6^′′ N, 10°34^′10^′′ E). The Glücksstern mine was operated for manganese and iron until its closure in 1855 (Scheven, 1990). The mine is also the type locality for crednerite, CuMnO₂ (Rammelsberg, 1849); gottlobite, CaMg(VO₄)(OH) (Witzke et al., 2000); vésigniéite, BaCu₃(VO₄)₂(OH)2 (Guillemin, 1955); and wakefieldite-(La) (Witzke et al., 2008). Plumbogottlobite is a late-stage, low-temperature hydrothermal mineral occurring on baryte and hausmannite.

Plumbogottlobite occurs as tablets, up to about 0.2 mm in diameter (Fig. 1). The mineral is identical in appearance to gottlobite. The tablets are flattened on {001} and exhibit the forms {100}, {010}, {001}, {110}, {011}, {101}, and {111} (Fig. 2). No twinning was observed. The colour is orange-brown, and the streak is light orange-brown. The mineral has adamantine lustre and is transparent. No fluorescence was observed in either long- or short-wave ultraviolet illumination. The Mohs hardness is about 4 to 4.5 based on scratch tests. The tenacity is brittle, and the fracture is irregular to conchoidal. The density could not be measured because crystals exceed the density of available density fluids. The density calculated from the empirical formula and single-crystal unit cell is 5.359 g cm⁻³. At room temperature, plumbogottlobite rapidly decomposes in dilute HCl, forming a white residue, which slowly dissolves.

Optically, plumbogottlobite crystals are uniaxial (–). The indices of refraction could not be measured because they are higher than available immersion liquids. The average index of refraction calculated from the Gladstone–Dale relationship (Mandarino, 1981) is 2.077. The 2V (meas.) was determined from extinction data, obtained on a spindle stage in a liquid of n=1.78 and analysed using EXCALIBRW (Gunter et al., 2004), is 84(1)°. The partially determined optical orientation is Y=c. No pleochroism was observed.

Crystals of plumbogottlobite were analysed at Caltech on a JEOL JXA-iHP200F field emission electron probe microanalyser (EPMA) in wavelength dispersive spectroscopy (WDS) mode (four points). The analytical conditions were 15 kV accelerating voltage, 10 nA beam current, and 5 µm beam diameter. Insufficient material is available for the determination of H₂O, and so it was calculated based on the structure (V = 1 and O = 5). No other elements were detected in energy-dispersive spectroscopy (EDS) analyses. The crystals did not take a good polish, which provided analyses that are estimated to be low by about 7.5 %. Consequently, the analyses have been normalised. Analytical data are given in Table 1.

The empirical formula (based on 5 O apfu), with cations allotted to structural sites, is (Pb_0.89Mn0.052+□0.06)_Σ1.00(Mg_0.77Cu0.192+Mn0.042+)_Σ1.00(VO₄)(OH) (+0.12 H for charge balance). The simplified formula is (Pb,Mn,□)(Mg,Cu,Mn)(VO₄)(OH), and the ideal formula is PbMg(VO₄)(OH), which requires PbO 61.41, MgO 11.09, V₂O₅ 25.02, and H₂O 2.48, totalling 100 wt %.

Raman spectroscopy was conducted on single-crystal fragments on a Horiba XploRA PLUS spectrometer using a 532 nm diode laser, 20 5 s accumulations at 2 mW power with a 100 µm slit, a 1800 grooves mm⁻¹ diffraction grating, and a 100× (0.9 NA) objective. The spectrum of plumbogottlobite from 4000 to 60 cm⁻¹ is compared with that of descloizite from Berg Aukas, Namibia (Natural History Museum of Los Angeles County, catalogue number 68303), in Fig. 3. Plumbogottlobite is very sensitive to the laser, requiring a relatively low power of 2 mW, whereas the descloizite spectrum was successfully recorded at 16 mW. The descloizite spectrum was chosen for comparison because of the mineral's similar composition, PbZn(VO₄)(OH), and equivalent structure.

The spectrum of plumbogottlobite is very similar to that of descloizite. A broad, weak band is seen in both spectra in the OH stretching region. The very weak feature at about 1550 cm⁻¹ is probably an overtone. Between 1000 and 200 cm⁻¹, both spectra are dominated by bands related to the stretching and bending vibrations of the VO₄ tetrahedron. The mode assignments shown in Fig. 3 are based on Frost et al. (2001), Martens et al. (2003), and Đorđević et al. (2016).

Plumbogottlobite has the same structure as descloizite, PbZn(VO₄)(OH), and other minerals with the descloizite structure type. It is the Pb analogue of gottlobite and the Mg analogue of descloizite; selected data are presented in Table 7. As noted by Đorđević et al. (2016), gottlobite, CaMg(VO₄)(OH), has an adelite-type structure with space group P2₁2₁2₁, which is topologically equivalent to the descloizite structure. Đorđević et al. (2016) noted that most phases with the descloizite–adelite structure topology that have the descloizite structure type are lead vanadates.

In the structure of plumbogottlobite, edge-sharing chains of MgO₄(OH)2 octahedra running parallel to [010] are corner-linked by VO₄ tetrahedra to form a three-dimensional framework. Cavities within the framework host Pb²⁺ cations. The Pb²⁺ is nine-coordinated, with three short bonds (2.37–2.47 Å) on one side and six longer bonds (2.73–3.23 Å) on the other, clearly showing the 6s² lone-pair electrons of Pb²⁺ to be stereoactive. The structure is shown in Fig. 4.