This special collection in Mineralogical Magazine honours Dr. Edward S. Grew’s long and distinguished career on the occasion of his 80^th birthday. The contributions stem from a dedicated session at the 4^th European Mineralogical Conference in Dublin (2024), held in celebration of Dr. Grew’s 80^th birthday. Together, these papers highlight the remarkable breadth of his scientific influence. The seventeen submissions reflect Ed’s wide-ranging interests and build on his legacy of discoveries spanning boron, lithium, and beryllium mineralogy; new mineral species and crystallography; rare-element geochemistry; the petrology of igneous and metamorphic rocks; and the changes of minerals through geologic time.

Minerals of the garnet supergroup hold a special place for Ed, owing in part to his key role in developing the most recent garnet nomenclature (Grew et al., Reference Grew, Locock, Mills, Galuskina, Galuskin and Hålenius2013). Fittingly, this volume includes two contributions that explore different aspects of garnet. The contribution of Galuskin et al. (Reference Galuskin, Galuskina, Kusz, Vapnik and Zieliński2025) presents the first terrestrial occurrence of the garnet species rubinite, Ca₃Ti³⁺₂Si₃O₁₂ previously known only from refractory inclusions in CV3 carbonaceous chondrites. It is considered a marker of extreme reducing conditions. In the pyrometamorphic Hatrurim Complex (Negev Desert, Israel), rubinite has been identified within a phosphide-bearing breccia formed when metasedimentary xenoliths underwent intense pyrometamorphism after being encased in a flamite–gehlenite paralava. In the confluence of garnets and rare earth elements, Harlov (Reference Harlov2025) demonstrates that at 900°C and 1000 MPa, experiments involving Y₂O₃, Sm₂O₃, LuPO₄, EuPO₄, and 2N NaOH produce rapid metasomatic incorporation of Y and REE into almandine–pyrope garnet by coupled dissolution–reprecipitation. These reactions modify the dodecahedral site through substitutions such as ^[8](Y,REE)³⁺ + ^[4]Al³⁺ = ^[8](Fe,Mg,Mn,Ca)²⁺ + ^[8]Si⁴⁺. In contrast to sluggish solid-state diffusion, this fluid-mediated process enables efficient Y + REE exchange in garnet during metamorphism, with important implications for Lu–Hf and Sm–Nd geochronology, Y–xenotime geothermometry, and the use of Y–δ¹⁸O systematics as a tracer of fluid–rock interaction. On a related note, priscillagrewite-(Y) is a Y-, Zr-bearing garnet (Ca₂Y)Zr₂Al₃O₁₂ (Galuskina et al., Reference Galuskina, Galuskin, Vapnik, Zeliński and Prusik2021).

Tourmaline, a boron-bearing mineral supergroup, has been a long-standing focus of Ed’s research (e.g. Grew, Reference Grew1988; Grew and Sandiford, Reference Grew and Sandiford1984; Grew et al., Reference Grew, Dymek, De Hoog, Harley, Boak, Hazen and Yates2015). Appropriately, four papers in this collection examine the occurrence, compositional diversity, and crystallographic systematics of tourmaline. Roach et al. (Reference Roach, Dutrow and Henry2025) describe an intricately zoned blue-grey tourmaline from the Dorothy China Clay Pit (St. Austell, UK) that records five discrete hydrothermal stages within a single crystal. Successive generations, each with distinct chemistry and species identity, include: (1) a rossmanite core (Li-rich, Na-poor); (2) elbaite; (3) Fe-rich schorl–foitite; (4) an Mg-rich dravite rim; and (5) fluor-schorl overgrowths. Textures reveal repeated dissolution–reprecipitation driven by evolving B-bearing fluids under changing pH and redox conditions. Tourmaline compositions track the progression of fluid compositions from Li-rich, Na-poor to Na–Fe-rich, later becoming more oxidising and Mg-enriched, and ultimately Fe–F-rich. The zoning sequence documents episodic open-system hydrothermal alteration and may reflect the broader kaolinsiation history of the St. Austell granite. A study by Zachař et al. (Reference Zachař, Škoda and Novak2025) found that early tourmaline crystallisation controls the formation of Be minerals in NYF pegmatites of the Třebíč Pluton (Czech Republic). Pegmatites with abundant early tourmaline host helvine–danalite ± phenakite, whereas those lacking tourmaline contain beryl ± phenakite. Early tourmaline incorporates Al, Mg, and Zn, depleting these elements from the melt while enriching the melt in Mn, favouring Mn-rich helvine–danalite. Consequently, the presence and composition of early tourmalines dictate the species and chemistry of subsequent Be-bearing minerals. The paper by Bačík and Ertl (Reference Bačík and Ertl2025) argues that short-range ordering in Li-bearing, Al-rich tourmaline controls the incorporation of Li in the Y site. If there is no Ca in the X site the Y-site Li atoms per formula unit (apfu) will be ≤ 1, consistent with synthetic tourmaline compositions. Higher Li contents can develop with addition of Ca in the X site. Higher ^YLi results in underbonding at the O1 site, favourable to incorporation of F, whereas more ^YAl in lower-Li tourmaline causes ‘overbonding’, which favours OH at the O1 site. Bosi et al. (Reference Bosi, Altieri, Skogby, Pezzottaa, Hålenius, Tempesta, Ballirano, Flégr and Cempírek2025) describe ferro-bosiite, a new Fe³⁺-dominant alkali-group tourmaline species from the Marina pegmatite, Mavuco, Alto Ligonha, Mozambique. It occurs as black acicular overgrowths at the analogous pole of a multi-coloured fluor-elbaite in a large collapsed pegmatitic cavity. The new species has an empirical formula: ^X(Na_0.99K_0.02)_Σ1.01 ^Y(Fe³⁺_1.56Mg_1.01Fe²⁺_0.20Ti_0.16)_Σ3.00 ^Z(Al_4.32Fe³⁺_0.41Fe²⁺_1.22)_Σ6.00 ^T(Si₆O₁₈) (BO₃)₃ (OH)₃ O[O_0.62(OH)_0.34F_0.04]_Σ1.00. Ferro-bosiite is the Fe²⁺ analogue of bosiite, marking a link in the oxy-dravite–dutrowite–bosiite solid-solution series. Ferro-bosiite formed from Fe- and Mg-rich B-bearing hydrothermal fluids following pegmatite-cavity collapse.

Beryllium-bearing minerals have long been central to Ed Grew’s research portfolio (e.g. Grew et al. Reference Grew, Yates, Shearer, Hagerty, Sheraton and Sandiford2006). In this context, the inclusion of a paper on beryl represents a particularly fitting contribution to the volume. Franz et al. (Reference Franz, Schiperski, Khmenko, Gernert and Nissen2025) describe beryl crystals from hydrothermal veins in the Colombian emerald district that exhibit complex growth and dissolution textures. Chemical analyses indicate minor substitution of Al by Na, Mg, and the chromophores V, Cr and Fe. All crystals display pronounced sector zoning, with Na and Mg enriched in the c-sector, and Al along with most trace elements, enriched in the a-sector. Overall, the textures indicate rapid skeletal growth along [0001], which governs the sector element distributions, and are broadly consistent with crystallisation reflecting closed-system behaviour.

Dr. Grew has been deeply engaged in the crystallography, discovery and identification of new and rare minerals, as well as in establishing robust mineral classifications (e.g. Grew et al. Reference Grew, Essene, Peacor, Su and Asami1991, Reference Grew, Armbruster, Medenbach, Yates and Carson2007, Reference Grew, Locock, Mills, Galuskina, Galuskin and Hålenius2013). Reflecting this central aspect of his career, six papers in the collection focus on these themes. Xiong et al. (Reference Xiong, Mugnaioli, Xu, Yang, Wirth, Franke and Grew2025) investigate two new Ti–Fe oxides, maurogemmiite (Ti₁₀Fe₃O₃) and paulrobinsonite (Ti₈Fe₄O₂), that occur in the alloy core of a zoned fragment from chromitite found in Luobusa, Tibet, China. These new species coexist with TiFe, osbornite, and α-Ti, rimmed by coesite, kyanite, and amorphous material. Maurogemmiite forms grains enclosed in paulrobinsonite. The α-Ti rim isolates the alloy core from outer coesite–kyanite zones, reflecting late contact between a mantle-derived alloy and crustal materials, consistent with mixed mantle–crust origin for the fragment. Juroszek et al. (Reference Juroszek, Krüger, Kolitsch, Frenz and Blaß2025) reports on the discovery of steiningerite, ideally Ba₂Zr₂(Si4O₁₂)O₂, in fissures of melilite nephelinite from the active Löhley quarry, Eifel Volcanic Field, Germany. The structure, isotypic with KTaSi₂O₇ and similar to rippite, comprises (Zr,Ti)O₆ chains linked by Si₄O₁₂ rings forming channels filled with Ba²⁺ and K⁺. The high-temperature occurrence and the H₂O-free associated minerals indicate formation under high-temperature pneumatolytic conditions. Welch et al. (Reference Welch, Najorka, Kleppe, Kampf and Spratt2025) describes nancyrossite, ideally FeGeO₆H₅, a new hydroxyperovskite discovered in samples from mineral species-rich Tsumeb, Namibia. The mineral forms through oxidation and partial dehydrogenation of stottite. Nancyrossite is tetragonal (P4₂/n), with cell parameters a = 7.37 Å and c = 7.30 Å and contains ∼88% Fe³⁺. The hydrogen appears to be dynamically distributed among six O atoms. Nancyrossite is the Ge-analogue of jeanbandyite, for which the idealised formula is proposed to be revised to FeSnO₆H₅. Holtstam et al. (Reference Holtstam, Camara, Karlsson and Zack2025) describe the rare Pb silicate jagoite, previously known only from Långban and Pajsberg, Sweden. It occurs with a diverse suite of Pb silicates, including several newly recognised mineral associations such as barysilite and melanotekite. These associated phases formed in skarn assemblages during metamorphism and were subsequently altered by Cl^–, SiO₂, Ca²⁺, and H₂O-rich fluids producing Pb silicates with elevated Si contents. The refined crystal structure of jagoite shows Fe³⁺ occupying three sites, with minor substitutions by Al, Mn³⁺, Zn, Mg, Ca and Na. Jagoite is paramagnetic down to 77 K and has the ideal formula Pb₁₁Fe₅Si₁₂O4₁Cl₃. Krivovichev et al. (Reference Krivovichev, Bindi and Hornfeck2025) note that the ET_n homological row represents a polysomatic series linking epidote-type (n = 0) and törnebohmite-type structures. The series encompasses members of the epidote (n = 0) and gatelite (n = 1) supergroups, as well as the radekškodaite group (n = 2). Their structures consist of alternating epidote (E) and törnebohmite (T) modules. The general formula for the series is A_2(n+1)M_n+3[Si₂O₇][SiO₄]_2n+1X_n+2 (X = O, OH, F). A structural model for the ET₃ member is proposed, extending the sequence beyond known compositions. The absence of members with n > 2 is attributed to entropic constraints and the principle of maximal structural simplicity that governs modular mineral architectures. Hawthorne (Reference Hawthorne2025) points out that the kröhnkite, talmessite, and fairfieldite groups, plus dondoellite, share the general formula X₂M²⁺(TO₄)₂(H₂O)₂ (X = Na, Ca; M²⁺ = Mg, Fe, Mn, Co, Ni, Zn, Cu; T = S, P, As) and are included in the IMA-approved kröhnkite supergroup. All have topologically identical chains; but differences reflect chain orientation and the hydrogen bonding. Structural stability follows the Lewis acidity–basicity correspondence principle: stable structures form when the acidity of the structural unit matches the basicity of the interstitial complex. For pentavalent T cations (P⁵⁺, As⁵⁺), Ca²⁺ provides the best match; for hexavalent T cations (S⁶⁺), Na⁺ gives the closest correspondence.

The study of minerals within their rock context has long been a cornerstone of Ed Grew’s scientific approach (e.g. Grew, Reference Grew1982, Grew et al., Reference Grew, Yates, Barbier, Shearer, Sheraton and Shiraishi2000, Reference Grew, Graetsch, Pöter, Yates, Buick, Bernhardt, Schreyer, Werding, Carson and Clarke2008). His meticulous optical observations lead to new species and novel interpretations of minerals, their assemblages and their environment of formation. In keeping with this tradition, three papers in the collection apply this petrologic–mineralogical perspective to illuminate mineral formation and evolution. Mitchell and Rodriguez Vega (Reference Mitchell and Rodriguez Vega2025) found that at the Sierra La Vasca Intrusive Complex (Mexican Eastern Alkaline Province), intrusion of silica-oversaturated alkaline-to-peralkaline granitoids into Cretaceous carbonates produced a unique cuspidine–hiortdahlite–wollastonite exoskarn. The skarn formed through the alteration of eudialyte, separation of Si-rich hydrothermal fluids and infiltration of Si–Zr–REE–P-bearing fluids. Zirconium was transported as Zr-fluoride and chloride complexes and reacted with calcite to form cuspidine–hiortdahlite solid solutions and wollastonite as the principal skarn minerals. Aleinikoff et al. (Reference Aleinikoff, Stoeser, du Bray, Holm-Denoma, Lowers and Thompson2025) examined zircons from the Jabal Radwa pluton, a peralkaline granite in the northwestern Arabian Shield. Separating the zircon populations based on colour, they could correlate colour with U/Pb age: dark brown grains (undatable), igneous tan and yellow grains (501–493 Ma), and green and blue xenocrystic grains (∼518 Ma or older). REE data define two groups: (1) HREE-enriched magmatic zircon (tan, yellow, brown) and (2) flat-pattern hydrothermal zircon (green, blue). Because regional magmatism ended near 570 Ma, the Radwa granite probably reflects post-shield magmatism related to eastern Egypt and later rift events associated with Oligocene opening of the Red Sea. Tuttle et al. (Reference Tuttle, Henry, Mogk, Mueller and Will2025) investigate a cordierite–orthopyroxene (COR) xenolith, enclosed in ∼2.80 Ga granitic rocks (Beartooth Mountains, Montana, USA), that preserves evidence for three distinct metamorphic events. The earliest, M1 granulite-facies assemblage (rutile–biotite–orthopyroxene–cordierite–quartz ± sillimanite), formed at ∼0.6 GPa and 775–815°C. Subsequent M2 upper-amphibolite-facies overprinting (∼0.4 GPa, 615–725°C) produced hydration of orthopyroxene to anthophyllite and induced plagioclase crystallisation. A final M3 greenschist-facies stage (<0.4 GPa, 500–600°C) generated talc and chlorite. The resulting clockwise P–T path records Archean arc-style compression, magmatic hydration, and later low-temperature alteration. The COR xenolith probably derived from a metasomatised basaltic protolith, consistent with other COR occurrences worldwide.

Ed’s interest in mineral evolution is a relatively recent addition to his nearly 60 year research portfolio, yet one in which he has made significant contributions (e.g. Grew et al., Reference Grew, Hystad, Toapanta, Eleish, Ostroverkhova, Golden and Hazen2019). In this volume, a new contribution by Bermanec (and the Mineralogical Society Hallimond Lecture) builds on this theme by examining key aspects of mineral ecology. Bermanec et al. (Reference Bermanec, Zhang, Downs, Kunić, Ma, Morrison, Prabhu and Hazen2025) analyse 4834 IMA-approved minerals and identified 87 essential mineral-forming ions. Using network and heat-map methods, they demonstrate that ions (1) form distinct groupings, (2) more strongly reflect igneous, hydrothermal, and weathering context rather than crystal-chemical limits, and (3) exhibit different geochemical affinities when present in multiple oxidation states. They also define ion antipathies—pairs or groups of ions that rarely occur together. For example, alkalis (Cs⁺, Li⁺, Rb⁺) seldom coexist with Ag⁺ or Cr⁶⁺. These patterns are interpreted as arising primarily from differences in geochemical availability and paragenetic incompatibilities rather than strict crystal-chemical limitations.

This special issue was made possible through the contributions of the authors and the generous time and effort of the Guest Editors: Barbara Dutrow, Gerhard Franz, Robert Martin and Jesse Walters; as well as the principal editors, Roger Mitchell and Stuart Mills. Most importantly, we extend our sincere gratitude to the production and managing editor, Helen Kerbey, who oversaw all aspects of the issue.