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Kopernikite; K(Ti7Cr3+)O16 – a new priderite-group mineral from the Morasko IAB-MG iron meteorite; Poland: 150 years of the Mineralogical Society: Past Discoveries and Future Frontiers
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DOI：10.1180/mgm.2026.10230.png)
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Abstract
En 中文
Kopernikite; K(Ti7Cr3+)O16 – 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 (I4/m; a = 10.0955(5) Å; c = 2.9534(2) Å; V = 301.01(4) Å3 and Z =1) for the grains with the composition (K1.12Ba0.23Ca0.03Na0.03)Σ1.42(Ti4+6.48Cr3+1.46Fe2+0.01 Al0.01)Σ7.96O16 based on 375 unique reflections to R1 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 VHN25 = 646(17) kg/mm2. 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.
Keywords:
new mineral
kopernikite
hollandite
priderite
Morasko
meteorite IAB
chromium
Poland
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