Rotherkopfite is the first member of the neptunite group that does not contain lithium in its chemical formula. It was found at Rother Kopf, Eifel volcanic fields, Germany, where in occurs in cavities in a quartz–sanidine fragment embedded in a volcanic rock. Rotherkopfite occurs as dark brownish-red crystals, up to about 0.2 mm across. The intriguing crystal structure is based on two interwoven three-dimensional frameworks.

The paper describes the characterisation of fluor-rewitzerite, a new mineral species belonging to the paulkerrite group. The crystal structure of fluor-rewitzerite has been refined using microfocus synchrotron diffraction data, which allowed 25 of the possible 30 H atoms to be located, thus establishing key features of the H bonding. Crystallochemical trends are reviewed for seven recently characterised monoclinic paulkerrite-group minerals.

We described two new minerals, igelströmite and manganoschafarzikite, from the Långban manganese–iron deposit in Värmland, Sweden. The chemical formulae are Fe³⁺(Sb³⁺Pb²⁺)O₄ and  Mn²⁺Sb³⁺₂O₄, respectively. They belong to a new mineral group, where all members have the same crystal structure. It is called the minium group, after the lead-oxide mineral that is the oldest known substance of this kind.

The first lanthanum-dominant mckelveyite group mineral, alicewilsonite-(YLa), Na₂Sr₂YLa(CO₃)₆∙3H₂O, was found at the Paratoo copper mine, South Australia, Australia.

Macraeite is the fourth type mineral to be described from the Mangualde pegmatite, Portugal, and is the first paulkerrite-group mineral to be characterised from the locality. Its crystal structure has been refined using synchrotron diffraction data, and its chemical analysis, Raman spectrum, and optical properties are reported.

The new mckelveyite group mineral bainbridgeite-(YCe) was found at Mont Saint-Hilaire, Quebec, Canada.

We report the description and the characterization of a new mineral species, found in a rock sample from the geological formation called the Pilanesberg Complex, South Africa. This is a silicate mineral that contains a significant amount of sodium, calcium, iron, titanium and fluorine. Its atomic structure shows that it is related to other wöhlerite-group minerals. This work provides new insights into the crystallization conditions that ruled the formation of the Pilanesberg complex.

The paper describes the formal establishment of the paulkerrite group of minerals and its nomenclature. It includes the application of a site-merging procedure, coupled with a site-total-charge analysis, to obtain unambiguous end-member formulae. Application of the procedure has resulted in the revision of the end-member formulae for several of the group members.

Regerite is the first new mineral species to be described from the Kreuzberg pegmatite, Pleystein, in the Oberpfalz, Bavaria. It has been characterised using electron microprobe analysis, Raman spectroscopy, optical measurements and a synchrotron-based single-crystal structure refinement. The structure type for regerite has not been previously reported.

Hochleitnerite is a new member of the paulkerrite group of minerals. Its crystal structure, chemical analyses and Raman spectroscopy are reported, and its crystallochemical properties are discussed in relation to other group members.

Manganrockbridgeite, Mn²⁺₂Fe³⁺₃(PO₄)₃(OH)₄(H₂O), a new member of the rockbridgeite group, has been characterised using electron microprobe analyses, Mössbauer spectroscopy, optical properties and single-crystal X-ray diffraction. Whereas other rockbridgeite-group minerals have orthorhombic symmetry with a statistical distribution of 50%Fe³⁺/50% vacancies in M3-site octahedra, monoclinic manganrockbridgeite has full ordering of Fe³⁺ and vacancies in alternate M3 sites along the 5.2 Å axis.

Pleysteinite has been approved as a new mineral species, and we describe here the characterisation of the mineral and its relationship to related minerals benyacarite, paulkerrite and mantienneite. The characterisation includes the determination and refinement of the crystal structure, electron microprobe analyses, optical properties and interpretation of its Raman spectrum.

Alicewilsonite-(YCe), a new mckelveyite group, was found at Mont Saint-Hilaire, Quebec, Canada, and subsequently at the Saint-Amable sill, Quebec, Canada, and the Khibiny Massif, Kola Peninsula, Russia.

A new mineral group – the mckelveyite group – consisting of seven carbonate minerals was established. One of the seven members, donnayite-(Y), was re-investigated and its belonging to the mckelveyite group was confirmed.

The paper gives a characterisation of the new mineral species, whiteite-(CaMnFe), which has recently been approved as a new mineral (proposal IMA2022-077). The study included a single-crystal structure refinement that, when combined with electron microprobe analyses, confirmed that the mineral was a new member of the whiteite subgroup of the jahnsite group of minerals. Relationships between the crystal structure and the unit-cell parameters for the whiteite-subgroup minerals are discussed.

First occurrences of the secondary phosphate minerals kenngottite, Mn₃²⁺Fe₄³⁺(PO₄)₄(OH)₆(H₂O)₂; allanpringite, Fe₃³⁺(PO₄)₂(OH)₃·5H₂O; iangreyite, Ca₂Al₇(PO₄)₂(PO₃OH)₂(OH,F)15·8H₂O; and nizamoffite, MnZn₂(PO₄)₂(H₂O)₄, from the Hagendorf Süd pegmatite are reported, with characterisation of their crystal chemistry and phase associations.

This paper describes the characterisation of a new mineral from a South Australian phosphate quarry. The characterisation included chemical analyses, infrared spectroscopy, and a determination and refinement of the crystal structure. The results showed that the mineral has a unique crystal chemistry, but it is closely related to the well-known phosphate mineral crandallite.

A reinvestigation of angastonite from the type locality has shown that it is a mixture of crystalline phases and an amorphous phase, with the published formula corresponding to the amorphous phase. A redefinition proposal for angastonite as an amorphous mineral was approved by the IMA CNMNC. Our study showed how the amorphous phase formed and how it progressively recrystallises as new crandallite-related minerals.