In this photo taken on the Isle of Elba in Italy you can see several radiating crystals of greenish Hedenbergite, inter-grown with blackish coloured Ilvaite in skarn bodies. Skarn is an unique formation that formed as a result of the interaction between geothermal fluids and the host rock. In this case the geothermal fluids come from the Late Miocene Porto Azzurro monzogranite, and Mesozoic marble, within which you can see skarns occurring as lens-shaped bodies.
Description by Samuele Papeschi, after the description on imaggeo.egu.eu.
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