Debattistiite, ideally Ag9Hg0.5As6S12Te2, is a new mineral (IMA-CNMNC 2011-098) from the Lengenbach quarry in the Binn Valley, Valais, Switzerland. It occurs as very rare tabular euhedral crystals up to 150 μm across in cavities in dolomitic marble, associated with realgar, rutile, trechmannite and hutchinsonite. Debattistiite is opaque with a metallic lustre and a grey streak. It is brittle; the Vickers hardness (VHN25) is 80 kg mm–2 (range: 65–94), corresponding to a Mohs hardness of 2–2½. In reflected light debattistiite is dark grey, highly bireflectant and weakly pleochroic from dark grey to a slightly greenish grey. Between crossed polars it is highly anisotropic with brownish to blue rotation tints. Internal reflections are absent. Reflectance percentages for the four COM wavelengths (Rmin and Rmax) are 27.2, 34.5 (471.1 nm), 25.5, 31.0 (548.3 nm), 22.9, 28.4 (586.6 nm), and 20.1, 25.2 (652.3 nm), respectively.

Debattistiite is triclinic, space group P1, with a = 7.832(5), b = 8.606(4), c = 10.755(5) Å, α = 95.563(9), β = 95.880(5), γ = 116.79(4)°, V = 635.3(6) Å3 and Z = 1. The crystal structure [R1 = 0.0826 for 795 reflections with I > 2σ(I)] consists of corner-sharing AsS3 pyramids forming three-membered distorted rings linked by Ag atoms in triangular or tetrahedral coordination.

The five strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are as follows: 10.56 (6) (001); 3.301 (5) (12); 2.991 (4) (22); 2.742 (1) and 2.733 (10) (30). A mean of nine electron microprobe analyses gave: Ag 44.88, Hg 4.49, As 20.77, S 17.72, Te 11.82; total 99.68 wt.%, which corresponds to Ag9.02Hg0.49As6.012S11.98Te2.01, on the basis of 29.5 atoms. The new mineral is named for Luca De Battisti, a systematic mineralogist and expert on the minerals of Lengenbach quarry.

The new mineral jakobssonite, ideally CaAlF5, was first found in crusts collected in 1988 from a fumarole on the Eldfell volcano, Heimaey Island, Iceland. It was subsequently found in similar crusts collected in 1991 from a fumarole on the Hekla volcano, Iceland. It is associated with leonardsenite (IMA2011-059), ralstonite, heklaite, anhydrite, gypsum, jarosite, hematite, opal and several fluoride minerals that have not been fully characterized. Jakobssonite occurs as soft white fragile crusts of acicular crystals <50 μm long. Its calculated density is 2.89 g cm–3. Chemical analyses by energy-dispersive spectrometry on a scanning electron microscope produced a mean elemental composition as follows: Ca, 18.99; Al, 18.55; Mg, 1.33; Na, 0.33; F, 50.20; O, 10.39; total 99.79 wt.%. The empirical chemical formula, calculated on the basis of 7 atoms per formula unit with all of the oxygen as OH, is (Ca0.73Mg0.09Na0.02)Σ0.84Al1.06F4.09(OH)1.01. Jakobssonite is monoclinic, space group C2/c, with a = 8.601(1), b = 6.2903(6), c = 7.2190(7) Å, β = 114.61(1)o, V = 355.09(8) Å3and Z = 4. The crystal structure contains chains of [AlF6] octahedra which run parallel to the c axis. These chains are interconnected by chains of [CaF7] pentagonal bipyramids. Jakobssonite is isostructural with several other CaMIIIF5 compounds. The eight strongest lines in the powder diffraction diagram [d in Å (I) (hkl)] are as follows: 4.91 (18) (110), 3.92 (76) (200), 3.15 (68) (020), 3.13 (100) (1), 2.27 (22) (2), 1.957 (21) (400), 1.814 (20) (1), 1.805 (22) (20). The chemical and crystal-structure analyses of jakobssonite are similar to synthetic CaAlF5 with minor substitutions of light elements (e.g. Na) or vacancies for Ca, and OH for F.

Xenotime-(Y), (Y,REE)PO4, and thortveitite, (Sc, Y)2Si2O7, in a miarolitic cavity in a niobium, yttrium, fluorine (NYF) granitic pegmatite at Baveno, Verbania, Southern Alps, Italy, were investigated by electron microprobe analysis and single-crystal X-ray diffraction. Fluorine has an important role as a complexing agent for Y and REEs in supercritical pegmatitic fluids; annitesiderophyllite and chamosite are the most likely sources of the Y and REEs. The thortveitite from Baveno contains up to 3.20 wt.% SnO2, an unusually high Sn content. Xenotime-(Y) is enriched in Gd in comparison to other Alpine xenotimes. Quantitative chemical data and measurements of the lattice parameters show that a higher scandium content results in a smaller unit-cell volume in thortveitite. The substitution of REEs for Y up to ∼20 mol.% has little effect on the unit cell of xenotime-(Y). The textures of xenotime-(Y) and thortveitite provide information about the dissolution and crystallization processes in the miarolitic cavity.

Forêtite, ideally Cu2Al2(AsO4)(OH,O,H2O)6, is a new secondary arsenate mineral from the Cap Garonne mine, Var, France (IMA2011-100). It has also been identified at the Salsigne gold mine, Languedoc-Roussillon, France. Although it was identified as a potentially new mineral in 1993, a formal description has only been possible as a result of a new find in a chamber called Annex S located near the entrance of the Cap Garonne mine. Forêtite occurs as pale sky blue to aqua aggregates, up to ∼0.1 mm across, made up of minute plates no more than 20 μm in length. It has a very pale blue streak. Individual crystals have a vitreous lustre and are transparent, whereas clusters appear translucent. The calculated density is 3.286 g cm–3. The crystals are brittle, with an irregular fracture and have a hardness of ∼3–4 on Moh's scale. Forêtite is found in direct association with bariopharmacoalumite, cyanotrichite, parnauite, chalcophyllite and mansfieldite in an Al-rich assemblage which is presumed to have formed under acidic conditions. It is biaxial; the average refractive index measured in white light on aggregates of forêtite crystals is 1.620(5). The empirical formula (based on 10 oxygen atoms per formula unit) is Cu1.94(Al1.96Fe0.04)Σ2.00(As0.84S0.09Si0.04)Σ0.97O10H5.19. Raman spectroscopy confirms the presence of OH and H2O in the structure. Forêtite is triclinic, space group P, with a = 6.969(9), b = 7.676(9), c = 8.591(11) Å, α = 82.01(9), β = 71.68(8), γ = 102.68(8)°, V = 415(1) Å3 and Z = 2. The five strongest lines in the X-ray powder diffraction pattern [d in A ˚ , (I), (hkl)] are as follows: 7.307, (100), (010, 00); 3.141, (24), (200, 00); 2.818, (24), (20, 20); 4.519, (23), (111); 2.343, (22), (11). The mineral is named in honour of Dr Jean-Paul Forêt, who co-founded the project that turned the Cap Garonne mine into a protected site and museum.

Understanding the environmental and biogeochemical behaviour of radionuclides is essential for managing our nuclear legacy safely. Remediation efforts and the concept of geological disposal of nuclear waste focus on immobilizing radionuclides within the subsurface. Here we review recent developments in the understanding of solid-phase capture processes of Cs, Sr, Tc, U, Pu and Np. Abiotic interactions between minerals and these radionuclides (including sorption, reductive precipitation and co-precipitation) have been studied in various conditions. Microbially driven processes are much less well characterized, for example the effects of microbial reduction on the structure and reactivity of existing minerals, or their role in the formation of new minerals. Metabolites released by bacteria can play a role in both mineral dissolution and formation, and better understanding their release and role in mineralization has great potential in the development of solid-phase capture processes for radionuclides.

With the aid of a map of the research landscape covered by this review (created using a cluster-analysis tool, a self-organizing map), we highlight the most promising sequestration processes for specific radionuclides. However, radionuclides exhibit highly species-specific behaviour in their interactions with minerals and microorganisms. More research is required to characterize the role mineral surfaces play in bioreductive immobilization of Pu and Np, the reduction products formed, and their relative stability. Further studies should concentrate on more environmentally relevant experiments that include bacteria, minerals and radionuclides.