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Spatial Macroscale Variability of the Role of Mineral Matter in Concentrating Some Trace Elements in Bituminous Coal in a Coal Basin—A Case Study from the Upper Silesian Coal Basin in Poland
Open AccessArticle

Greenockite Whiskers from the Bytom Burned Coal Dump, Upper Silesia, Poland

Institute of Earth Sciences, Faculty of Natural Sciences, University of Silesia, Bankowa 12, 40-007 Katowice, Poland
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Minerals 2020, 10(5), 470; https://doi.org/10.3390/min10050470
Received: 3 April 2020 / Revised: 19 May 2020 / Accepted: 20 May 2020 / Published: 22 May 2020
(This article belongs to the Collection Minerals in Coal and Coal Combustion Products)
Orange greenockite (CdS) aggregates were found in a small fumarole at a burned coal dump near Bytom, Upper Silesia, Poland and were studied using a variety of techniques in order to determine their chemistry, morphology, and most importantly, the mechanism of crystal growth. Greenockite rods, wires, and whiskers with bismuth drops on crystal tops are predominant in these aggregates. Greenockite rods oriented sub-perpendicular to the substrate surface. The rod thickness reaches 5–6 μm and about 10 μm in length. The catalyst bismuth drop has a diameter comparable to the rod thickness. Fiber forms (wires and whiskers) are sub-parallel to the substrate surface. The thickness of these forms is usually less than 2 μm, and the length can be close to 1 mm. The bismuth drop diameter can show a large excess over the fiber thickness. Catalyst drops on the tops of whiskers began to change their form dynamically and exploded, spraying bismuth under the electron beam effect. Rods grow along the [01–10] direction, and whiskers and wires (axial forms) along the [0001] direction. Greenockite rod crystals, carrying on top a relatively homogenous bismuth catalyst drop, were formed on the heated substrate according to the VLS (vapor–liquid–solid) mechanism at temperatures not lower than 270 °C. Greenockite whiskers and wires grew just above of the substrate surface according to the VQS (vapor–quasiliquid–solid) mechanism at temperatures lower than 200 °C. These mechanisms of growth have very rarely been recorded to occur in nature and even less so in burning coal dumps. The cooperative growth effects of the fiber greenockite crystals were also described. View Full-Text
Keywords: greenockite; whisker; bismuth drop; VLS mechanism; VQS mechanism; coal dump; Bytom; Poland greenockite; whisker; bismuth drop; VLS mechanism; VQS mechanism; coal dump; Bytom; Poland
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MDPI and ACS Style

Nowak, K.; Galuskina, I.; Galuskin, E. Greenockite Whiskers from the Bytom Burned Coal Dump, Upper Silesia, Poland. Minerals 2020, 10, 470.

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