October 2026 IMA Newsletter 93 & 92 Breakthroughs: Wusiheite (Germanium Benitoite), Zhaoyuanite, Carolinaite & Wolfgangpauliite
Direct Crystallographic & Collector Mineralogy Summary: In October 2026, the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA-CNMNC Newsletter 93, European Journal of Mineralogy 38:629–633, Oct 16, 2026, & Newsletter 92) approved a remarkable suite of rare collector and critical-element minerals. Foremost among them is Wusiheite (BaGe(Ge3O9), IMA 2025-083a) from the Wusihe Pb–Zn deposit in Sichuan, China—discovered to be the Germanium–Germanium analog of California's state gemstone, Benitoite (BaTi(Si3O9)). In Wusiheite, tetravalent Germanium (Ge4+) simultaneously forms three-membered [Ge3O9]6− rings and isolated [GeO6]8− octahedra in trigonal space group P321. Newsletter 93 and 92 also unveiled Zhaoyuanite (MnZnTe4+4O10, IMA 2026-006) from the famous Moctezuma tellurium mine in Sonora, Mexico; Carolinaite ([Cu4Pb4O2(OH)8(SO4)(H2O)2]·(SO4)(H2O)2, IMA 2026-001) from North Carolina; Wolfgangpauliite (Ca2K(H2O)11[(UO2)6O4(PO4)4], Oct 2026) honoring quantum physicist Wolfgang Pauli; and Bromammoniac (NH4Br, IMA 2025-103a) from an active burning shale vent in Santa Barbara, California.
🔬 Gladstone-Dale Compatibility, Cauchy Dispersion & Ring Expansion Equations
- Gladstone-Dale Law of Mineral Refractive Index (n̄) & Mandarino Compatibility Index (CI):
(n̄ − 1) / ρ = K_P = ∑ (k_i · wt%_i / 100)|CI = 1 − (K_P / K_C) - Cauchy Optical Dispersion & B–G Fire (n430.8nm − n686.7nm):
n(λ) = A + B / λ² + C / λ⁴→ High in Ge4+, Ti4+, Te4+ & Pb2+ minerals - Benitoite [Si3O9]6− to Wusiheite [Ge3O9]6− Ring Bond Expansion:
d(Si–O) ≈ 1.62 Å → d(Ge–O) ≈ 1.75 Å (Tetrahedral) & 1.89 Å (Octahedral GeO₆)
Complete Reference Chart: 8 Newly Approved 2026 IMA Collector Minerals
| Mineral Name & IMA No. | Chemical Formula | Symmetry & Unit Cell | Type Locality & 2026 Discovery Significance |
|---|---|---|---|
WusiheiteIMA 2025-083a (Oct 2026) | BaGe(Ge₃O₉) | Trigonal P321a = 11.7492 Å, c = 4.76 Å | Wusihe Pb–Zn deposit, Sichuan, China; Ge–Ge analog of Benitoite (Wen, Zhu, He et al., Oct 2026) |
ZhaoyuaniteIMA 2026-006 (2026) | MnZnTe⁴⁺₄O₁₀ | Tetragonal P4₂/nbca = 8.7199 Å, c = 12.9067 Å | Moctezuma mine, Sonora, Mexico; denningite-related lone-pair tellurite (Yang, Downs et al., 2026) |
CarolinaiteIMA 2026-001 (Oct 2026) | [Cu₄Pb₄O₂(OH)₈(SO₄)(H₂O)₂]·(SO₄)(H₂O)₂ | Monoclinic P2/ca = 13.629 Å, b = 7.311 Å | Redmond mine, Haywood Co., North Carolina; new structure type (Emproto, Olds, Kampf et al., Oct 2026) |
WolfgangpauliiteCNMNC NL 93 (Oct 2026) | Ca₂K(H₂O)₁₁[(UO₂)₆O₄(PO₄)₄] | Monoclinic C2/ma = 13.6449 Å, b = 15.0 Å | Related to françoisite-(Ce); honors Nobel physicist Wolfgang Pauli (Plášil, Škoda, Meisser, Oct 2026) |
BromammoniacIMA 2025-103a (Oct 2026) | NH₄Br | Cubic Pm3̄ma = 4.0161(2) Å | Burning bituminous shale vent, Hope Ranch sea cliff, Santa Barbara, CA; Br analog of salammoniac |
Rozhdestvenskayaite-(Fe)IMA 2026-025 (Oct 2026) | Ag₆(Ag₄Fe₂)Sb₄S₁₂S | Cubic I4̄3ma = 10.9102(8) Å | Bianjiadayuan Ag–Pb–Zn deposit, China; ultra-silver-rich tetrahedrite member (Gu et al., Oct 2026) |
SainzbarandaiteIMA 2026-024 (Oct 2026) | Ca₇Al₄F₂₆(H₂O)₅ | Monoclinic P2₁/ca = 12.1062 Å, b = 6.8 Å | Qinglong Sb mine, Guizhou, China; complex aluminofluoride related to gearksutite (Grey, Kampf et al.) |
SakhanaiskiteIMA 2026-008 (2026) | (Fe²⁺Ti)Nb₂O₈ | Monoclinic P2/ca = 4.7469 Å, b = 5.7275 Å | Sakhanaiskiy granite massif, Siberia; ordered columbite-supergroup niobate (Chukanov, Pekov et al.) |
Frequently Asked Questions
Why is Wusiheite (BaGe(Ge₃O₉)) such a major discovery for crystal chemistry?
Classic Benitoite (BaTi(Si3O9)) requires two different tetravalent cations of different ionic radii: smaller Si4+ (0.26 Å) in 4-coordinated tetrahedral rings and larger Ti4+ (0.605 Å) in 6-coordinated octahedra. Germanium (Ge4+) sits at the exact Goldilocks radius where it can adopt both 4-fold tetrahedral coordination (0.39 Å) and 6-fold octahedral coordination (0.53 Å) simultaneously in the same crystal—allowing Wusiheite to build a pure barium-germanate benitoite framework in nature.
How did Bromammoniac (NH₄Br) form on a California beach cliff in 2026?
Described in the October 16, 2026 IMA-CNMNC Newsletter 93 (IMA 2025-103a), Bromammoniac was discovered sublimating directly around an active natural gas/fumarole vent in burning organic-rich bituminous shale of the Monterey Formation on a sea-cliff talus slope at Hope Ranch in Santa Barbara, California. Marine bromine and organic nitrogen from the burning shale combined with sea-spray halides to crystallize cubic CsCl-structured NH4Br crystals (a = 4.0161 Å).
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