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Feather preservation fabrics. (a) Contour/down feathers preserved by silica encrustation. (b) Flight feather moulds fractured to reveal a fine layer of carbon grains. (c) Light microscope image of plumage encrusted by glassy silica. (d) Scanning electron photomicrograph of external feather mould, fractured to reveal internal surfaces, r, rachis; b, barbs. Botryoidal silica fabric of external surface comprises partly coalesced silica particles.
