Platinum football – created by nature
"The FIFA World Cup has just started when I was busy in the lab investigating a heavy mineral concentrate from a chromitite sample, and found this fantastic example of an euhedral grain of sperrylite (PtAs2) – resembling a football but only 50 µm in size”, says PhD student Matías Garcia Tudela from Applied Geochemistry.
The platinum-group mineral (PGM) in the image shows a perfect cubo-octahedral morphology as sperrylite crystallizes in the isometric crystal system. Sperrylite can be found associated to several geological environments but is mainly found in magmatic (ultramafic-mafic intrusions) as well as in alluvial deposits related to these intrusions. The “sperrylite football”, in the size of a human´s hair diameter, was discovered in a heavy mineral concentrate obtained via hydroseparation of a crushed and sieved chromitite sample from the Cabo Ortegal Complex (Spain).
What is hydroseparation?
The hydroseparation process is a water-based and hence environmentally friendly method to obtain heavy mineral concentrates following the physical principles of the “stokes-law”. The process includes pulses of water that simulate waves from a natural beach placer deposit. LTU has such a hydroseparation facility within the quantitative target mineralogy (QanTmin) laboratories at Applied Geochemistry. After the successful separation, the sperrylite grain was investigated via scanning electron microscopy (SEM) at the QanTmin labs.
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