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February 1, 2017 at 11:38 am #18483
Again, @jayson-kowinsky can likely provide more detail, but I’m thinking you’re looking at calcite (or quartz) veins within the shale. You can get dendrites (non-fossil crystal growths) of calcite and other minerals on parallel surfaces like shale layers or some fine-grained limestones. As for why the shale is black, it is likely due to high organic content when the layers were deposited.