An extremely rare mercury iodide coccinite, HgI2, was found in a burning dump of the Almaznaya coal mine (near the settlement of Gukovo, Rostov oblast, Russia). It forms bright red tabular and short-prismatic crystals with adamantine luster up to 0.5 mm in size on a crust of native sulfur, which flls the fractures in the burnt rock. This is the frst fnd of coccinite in the Russian Federation. The refectance values and quantitative chemical analysis of coccinite are published for the frst time. The chemical composition of the mineral is as follows (wt. %, mean of fve analyses, electron microprobe): Hg 45.15, Cl 0.11, Br 0.65, I 53.91, total 99.82. The empirical formula calculated based on sum of three atoms is Hg1.02I1.93Br0.04Cl0.01. The strongest refections of the powder X-ray diffraction diagram are [d,A(I)(hkl)]: 6.220(29)(002), 4.122(82) (101), 3.575(100)(102), 3.008(37)(103), 2.767(35)(112), 2.189(98)(114, 200). The parameters of the tetragonal unit cell calculated from the powder data are as follows: a = 4.3744(2), c = 12.4301(7) A, V = 237.86(2) A3. Coccinite crystallized from hot gases after the combustion of coal-bearing rocks in the inner part of the dump.

Keywords: coccinite, mercury iodide, frst fnd in Russia, burning dump, Almaznaya coal mine, Eastern Donbass.

Funding. The X-ray diffraction study was carried out in the Research Centre for X-ray Diffraction Studies of the St. Petersburg State University (St. Petersburg) in accordance with state contract no. AAAA-A19-119091190094.

Acknowledgements. We are grateful to Mikhail M. Bitman, Alexander I. Tishchenko and Nikita V. Chukanov for the help with literature and discussion. The authors are also thankful to an anonymous reviewer for constructive comments.

Confict of interest. The authors declare that they have no conficts of interest.

Author contribution. A.V. Kasatkin – conceptualization, physical properties, optical data, chemical analyses, writing of the manuscript; I.V. Pekov – X-ray data, SEM photo, writing of the manuscript; O.V. Trofmov – feld works, literature data, writing of the manuscript; A.A. Agakhanov – analytical works; M.D. Milshina – literature data, preparation of fgures; S.N. Britvin – X-ray diffraction study. All the authors approved the fnal version of the manuscript prior to publication.

For citation: Kasatkin A.V., Pekov I.V., Trofmov O.V., Agakhanov A.A., Milshina M.D., Britvin S.N. Coccinite from the burning dump of Almaznaya coal mine (Eastern Donbass) – the frst fnd in Russia. Mineralogy, 2025, 11(1), 5–21. DOI: 10.35597/2313-545X-2025-11-2-1

Received 03.02.2025, revised 11.02.2025, accepted 14.04.2025

A.V. Kasatkin, Fersman Mineralogical Museum RAS, Moscow, Russia;
anatoly.kasatkin@gmail.com

I.V. Pekov, Moscow State University, Moscow, Russia;

O.V. Trofimov, Rostov-on-Don, Russia;

A.A. Agakhanov, Fersman Mineralogical Museum RAS, Moscow, Russia;

M.D. Milshina, Moscow,  Russia;

S.N. Britvin, St. Petersburg State University,  St. Petersburg, Russia

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