A new mineral species, guangyuanite, ideally Pb3Cl3(Se4+O3)(OH), was discovered from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. It occurs as equant crystals. Associated minerals are Co-bearing krut'aite–penroseite, chalcomenite, schmiederite, olsacherite, phosgenite, anglesite, cerussite and franksousaite. Guangyuanite is pale yellow–brown in transmitted light, transparent with white streak and vitreous lustre. It is brittle and has a Mohs hardness of ~3. No parting or cleavage was observed. The calculated density is 7.63 g/cm3. An electron microprobe analysis yielded an empirical formula [based on 7 (O + Cl) atoms per formula unit] of Pb3.02Cl3.01(Se4+0.99O3)(OH), which can be simplified to Pb3Cl3(Se4+O3)(OH).

Guangyuanite is isostructural with synthetic Pb3Br3(Se4+O3)(OH). It is orthorhombic, with space group Pnma and unit-cell parameters a = 11.0003(5), b = 10.6460(5), c = 7.7902 Å, V = 912.31(6) Å3 and Z = 4. The crystal structure of guangyuanite contains two symmetrically-distinct Pb (Pb1 and Pb2) cations, with Pb1 coordinated by eight anions (4O + 4Cl) and Pb2 only by six anions (3O + 3Cl), forming a marked lopsided coordination typical of Pb2+ with a stereochemically active 6s2 lone electron pair. The Se4+ cation forms a typical [Se4+O3] trigonal pyramid. The crystal structure of guangyuanite can be described as consisting of layers of edge-sharing [Pb1O4Cl4] polyhedra parallel to (100). These layers are linked together by sharing polyhedral corners (Cl atoms), as well as [Pb2O3Cl3] and [Se4+O3] groups. Chemically, guangyuanite is one of six lead chloride selenite minerals reported thus far and closely related to orlandiite Pb3Cl4(Se4+O3)⋅H2O.

A new mineral species, mikenewite (IMA2022-102), ideally Mn2+(S4+O3)⋅3H2O, has been discovered from the San Judas Chimney, Ojuela mine, Mapimí, Durango, Mexico. It occurs as spheres of platy crystals. Associated minerals include goethite, cryptomelane, adamite and lotharmeyerite. Mikenewite is yellowish in transmitted light, transparent with a white streak and vitreous lustre. It is brittle and has a Mohs hardness of 2½–3. Cleavage is perfect on {101}. The measured and calculated densities are 2.48(5) and 2.467 g/cm3, respectively. Optically, mikenewite is biaxial (+), with α = 1.606(5), β = 1.614(5), γ = 1.627(1) (white light), 2V(meas.) = 69(3)° and 2V(calc.) = 77°. An electron microprobe analysis yielded an empirical formula (based on 6 O apfu) of (Mn0.86Zn0.12Fe0.04Ca0.02)Σ1.04(S0.98O3)⋅3H2O, which can be simplified to (Mn,Zn,Fe)(SO3)⋅3H2O.

Mikenewite is the natural analogue of synthetic α-Mn2+(S4+O3)⋅3H2O, as well as the Mn-analogue of albertiniite, Fe2+(S4+O3)⋅3H2O. It is monoclinic, with space group P21/n and unit-cell parameters a = 6.6390(3), b = 8.8895(4), c = 8.7900(4) Å, β = 96.095(2)°, V = 515.83(4) Å3 and Z = 4. The crystal structure of mikenewite is characterised by each Mn atom coordinated octahedrally by six O atoms, three from different sulfite O atoms and three from H2O molecules. Each S4+O3 group is bonded to three Mn atoms, resulting in a sheet parallel to (101) with the sheet composition of Mn2+(S4+O3)⋅3H2O. Such sheets, stacked along [10$\bar{1}$], are joined together by hydrogen bonds, accounting for the perfect cleavage of the mineral. Mikenewite is dimorphous with orthorhombic Pnma gravegliaite, as albertiniite is with fleisstalite. Its discovery from the Ojuela mine, which is particularly rich in Zn, implies the possibility of finding Zn-bearing sulfites there as well.

A new mineral species, bernardevansite (IMA2022-057), ideally Al2(Se4+O3)3⋅6H2O, has been discovered from the El Dragón mine, Potosí Department, Bolivia. It occurs as aggregates or spheres of radiating bladed crystals on a matrix consisting of Co-bearing krut'aite–penroseite. Associated minerals are Co-bearing krut'aite–penroseite, chalcomenite and ‘clinochalcomenite’. Bernardevansite is colourless in transmitted light, transparent with white streak and vitreous lustre. It is brittle and has a Mohs hardness of 2½–3. Cleavage is not observed. The measured and calculated densities are 2.93(5) and 2.997 g/cm3, respectively. Optically, bernardevansite is biaxial (+), with α = 1.642(5), β = 1.686(5) and γ = 1.74(1) (white light). An electron microprobe analysis yielded an empirical formula (based on 15 O apfu) (Al1.26Fe3+0.82)Σ2.08(Se0.98O3)3⋅6H2O, which can be simplified to (Al,Fe3+)2(SeO3)3⋅6H2O.

Bernardevansite is the Al-analogue of mandarinoite, Fe3+2(SeO3)3⋅6H2O or dimorphous with P$\bar{6}$2c alfredopetrovite. It is monoclinic, with space group P21/c and unit-cell parameters a = 16.5016(5), b = 7.7703(2), c = 9.8524(3) Å, β = 98.258(3)°, V = 1250.21(6) Å3 and Z = 4. The crystal structure of bernardevansite consists of a corner-sharing framework of M3+O6 (M = Al and Fe) octahedra and Se4+O3 trigonal pyramids, leaving large voids occupied by the H2O groups. There are two unique M3+ positions: M1 is octahedrally coordinated by (4O + 2H2O) and M2 by (5O + H2O). The structure refinement indicates that Al preferentially occupies M1 (= 0.692Al + 0.308Fe) over M2 (= 0.516Al + 0.484Fe). The substitution of the majority of Fe in mandarinoite by Al results in a significant reduction in its unit-cell volume from 1313.4 Å3 to 1250.21(6) Å3 for bernardevansite. The discovery of bernardevansite begs the question whether the Fe3+ end-member, Fe3+2(SeO3)3⋅6H2O, has two polymorphs as well, one with P21/c symmetry, as for mandarinoite and the other P$\bar{6}$2c, as for alfredopetrovite.

A new beryllophosphate mineral species, loomisite (IMA2022-003), ideally Ba[Be2P2O8]⋅H2O, was found from the Big Chief mine near Keystone, Pennington County, South Dakota, USA. It occurs as divergent sprays of very thin bladed crystals with a tapered termination. Individual crystals are found up to 0.80 × 0.06 × 0.03 mm. Associated minerals include dondoellite, earlshannonite, mitridatite, rockbridgeite, jahnsite-(CaMnFe) and quartz. No twinning or parting is observed macroscopically. Loomisite is murky white in transmitted light, transparent with white streak and silky to vitreous lustre. It is brittle and has a Mohs hardness of 3½–4, with perfect cleavage on {100} and {$\bar{1}$10}. The measured and calculated densities are 3.46(5) and 3.512 g/cm3, respectively. Optically, loomisite is biaxial (+), with α = 1.579(5), β = 1.591(5), γ = 1.606(5) (white light), 2V (meas.) = 82(2)° and 2V (calc.) = 85°. It is non-pleochroic under polarised light, with a very weak (r > v) dispersion. The mineral is insoluble in water or hydrochloric acid. An electron microprobe analysis, along with the BeO content measured with an ICP-MS, yields an empirical formula (based on 9 O apfu) (Ba0.96Ca0.06)Σ1.02[(Be1.96Fe0.06)Σ2.02P1.99O8]⋅H2O, which can be simplified to (Ba,Ca)[(Be,Fe)2P2O8]⋅H2O.

Loomisite is monoclinic, with space group Pn and unit-cell parameters a = 7.6292(18), b = 9.429(2), c = 4.7621(11) Å, β = 91.272(5)°, V= 342.47(14) Å3 and Z = 2. Its crystal structure is characterised by a framework of corner-sharing PO4 and BeO4 tetrahedra. The framework can be considered as built from the stacking of sheets consisting of 4- and 8-membered rings (4.82 nets) along [001] or hexagonal layers (63 nets) along [010]. The extra-framework Ba2+ and H2O are situated in the channels formed by the 8-membered rings. Topologically, loomisite represents the first natural example with the zeolite ABW-type framework, which is adopted by over 100 synthetic compounds with different chemical compositions.

A new mineral species, franksousaite (IMA2021-096), ideally PbCu(Se6+O4)(OH)2, has been found from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. It occurs as short prismatic crystals included in colourless anglesite. Associated minerals are Co-bearing krut'aite–penroseite, chalcomenite, schmiederite, olsacherite, phosgenite, anglesite and cerussite. Franksousaite is blue in transmitted light, transparent with very pale blue streak and has a vitreous lustre. It is brittle and has a Mohs hardness of 2–2½. Cleavage is perfect on {100}. The calculated density is 5.64 g/cm3. An electron microprobe analysis yielded an empirical formula (based on 6 O apfu) of Pb1.02Cu0.98[(Se0.84S0.17)Σ1.01O4)](OH)2, which is simplified to PbCu[(Se,S)O4)](OH)2.

Franksousaite is the Se6+ analogue of linarite, PbCu(SO4)(OH)2. It is monoclinic, with space group P21/m and unit-cell parameters a = 9.8208(3), b = 5.7340(2), c = 4.74980(10) Å, β = 102.683(2)°, V = 260.947(13) Å3 and Z = 2. The crystal structure of franksousaite consists of Jahn-Teller-distorted Cu2+O6 square bipyramids, which form chains along b by sharing trans edges across their square planes. The chains are decorated by SeO4 tetrahedra and linked to one another by hydrogen bonds to form layers parallel to (100). These layers are bound together by double layers of PbO8 and SeO4 polyhedra. The PbO8 polyhedron exhibits one-sided coordination typical of Pb2+ with a stereochemically active 6s2 lone-electron-pair. The major structural difference between franksousaite and linarite lies in the <Se–O> vs. <S–O> bond distances (1.615 vs. 1.482 Å), accounting for the larger unit-cell volume for franksousaite. A comparison of Raman spectra for the four minerals in the linarite group (linarite, franksousaite, munakataite and schmiederite) reveals the obvious differences among them, especially in the range from 700 to 1000 cm–1, indicative of the presence or absence of (Se4+O3)2–, (Se6+O4)2–, and/or (SO4)2– groups.

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