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Geology, Palaeontology & Archaeology / What causes this colouration in a piece of slate?
« on: 24/05/2016 00:44:23 »
A mate handed me this to see if I could give an explanation of the coloration on the surface of this low grade slate. Apparently from a thin lens in a larger bed of folded (this bed at 90 deg) marine sediments (some of shallow marine volcanics) - hard to see in the photos i guess but I notices some cross bedding in one of the sub-layers of this specimen, I'm guessing of fan deposit.
The interesting bit is the coloration on the surface of fresh specimens. It has an 'opaline' or 'oil slick' appearance. Can't be seen when wet with water or lacquer. Crosses the layers within the specimen. Any suggestions!? Cheers!
Pictures hopefully attached
The interesting bit is the coloration on the surface of fresh specimens. It has an 'opaline' or 'oil slick' appearance. Can't be seen when wet with water or lacquer. Crosses the layers within the specimen. Any suggestions!? Cheers!
Pictures hopefully attached