2026/05/05 by Evgeny V. Galuskin, Evgeny Galuskin ・・・・・・, Andrzej Muszyński +5
Materials Science · Physics and Astronomy · #Astro and Planetary Science #Crystal Structures and Properties #Planetary Science and Exploration
paper · doi:10.1180/mgm.2026.10230
crossref issued 2026/05/05 · crossref published 2026/05/05 · crossref published-online 2026/05/05 · openalex publication_date 2026/05/05 · crossref created 2026/05/05 · openalex created_date 2026/05/06 · crossref published-print 2026/06/01 · openalex updated_date 2026/06/24 · crossref deposited 2026/07/17 · crossref indexed 2026/07/30
Abstract Kopernikite, K(Ti 7 Cr 3+ )O 16 – a new mineral belonging to the priderite group with a hollandite-type structure, was discovered within a graphite–troilite nodule in the Morasko iron meteorite of the IAB-MG type. This meteorite fell in the territory of modern-day Poland around 5000 years ago. Kopernikite is confined to the external graphite zone of the nodule and intergrows with fluorapatite. The kopernikite structure was refined ( I 4/ m, a = 10.0955(5) Å , c = 2.9534(2) Å, V = 301.01(4) Å 3 and Z =1) for the grains with the composition (K 1.12 Ba 0.23 Ca 0.03 Na 0.03 ) Σ1.42 (Ti 4+ 6.48 Cr 3+ 1.46 Fe 2+ 0.01 Al 0.01 ) Σ7.96 O 16 based on 375 unique reflections to R 1 value of 0.018. The colour of kopernikite changes from dark green in massive grains to yellow–green in thin grains, and the streak is light green. The mineral has a vitreous lustre and a hardness of ∼5.5 on the Mohs scale, as calculated on the basis of microhardness VHN 25 = 646(17) kg/mm 2 . The Raman spectrum of kopernikite is similar to that of priderite. Kopernikite crystallised from drops of phosphate melt simultaneously with fluorapatite at a temperature of 1000°C, due to the local enrichment of the melt with K, Ba, Ti and Cr. The increased amount of tunnel cations in the kopernikite structure (∼1.4–1.5 apfu), as calculated from microprobe analyses, exceeds the theoretically possible value of 1.33 apfu for minerals of the priderite group. This increase can be attributed to formation of kopernikite under the increased pressure, as well as artefacts that appear when the mineral composition is measured using a microprobe analyser.