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Updated: October 14, 2026
I can understand these facts, namely, the blending of the jasper into the semi-decomposed basalt, its occurrence in angular patches, which clearly do not occupy pre-existing hollows in the rock, and its containing little vesicles filled with chalcedony, like those in the scoriaceous lava, only on the supposition that a fluid, probably the same fluid which deposited the chalcedony in the air-cells, removed in those parts where there were no cavities, the ingredients of the basaltic rock, and left in their place silica and iron, and thus produced the jasper.