2025/09/17 by Thomas Malcherek, Boriana Mihailova, Jochen Schlüter +2
Chemistry · Environmental Science · Materials Science · #Chemical Synthesis and Characterization #Crystal Structures and Properties #Inorganic Fluorides and Related Compounds
paper · pdf · doi:10.1180/mgm.2025.10157
crossref issued 2025/09/17 · crossref published 2025/09/17 · crossref published-online 2025/09/17 · openalex publication_date 2025/09/17 · crossref created 2025/09/17 · openalex created_date 2025/10/10 · crossref deposited 2026/07/23 · openalex updated_date 2026/07/24 · crossref indexed 2026/07/30
Abstract Metaheimite (IMA 2023-020a), PbCu 2 (AsO 4 )(OH) 3 , has been identified as a new secondary mineral at the Grosses Chalttal deposit, Mürtschenalp district, Glarus, Switzerland. It forms radial aggregates of blade-like crystals of light blue to turquoise blue colour. Metaheimite has a light blue streak and vitreous to silky lustre. Its calculated density is 5.47 g cm –3 . The empirical chemical formula based on seven anions per formula unit is (Pb 0.96 Ca 0.03 )Cu 1.98 (As 1.01 O 4 )(OH) 3 . Metaheimite is pseudo-orthorhombic, with monoclinic symmetry, space group P 2 1 /n and unit cell parameters a = 5.8347(4), b = 7.7528(6), c = 13.8899(9) Å, β = 90.018(3)°, V = 628.31(8) Å 3 and Z = 4. The five strongest lines in the calculated powder diffraction pattern are ( d in Å(I) hkl ) as follows: 6.945(100)002, 3.870(75)112, 3.169(78)014, 3.145(99)121 and 2.615(81)015. The crystal structure, refined to R obs = 6.13% for 1393 reflections with I > 3σ( I ), consists of layers similar to those occurring in heimite, PbCu 2 (AsO 4 )(OH) 3 ·2H 2 O, but with 6+2 coordinated Pb 2+ . The lack of water molecules in metaheimite causes different interlayer hydrogen bonding and consequently, different layer stacking order as compared to that in heimite. In metaheimite, Cu 2+ therefore occurs in a square-pyramidal coordination by five oxygen atoms. Hydrous species in metaheimite have been examined by Raman and by infrared spectroscopy. Metaheimite is structurally related to duftite, PbCu(AsO 4 )(OH) and may be considered a transitional state between heimite and duftite.