Feather fibers are not tissue, any more than hair is tissue. However blood vessels would be. If it's tissue, the question would be easy to answer. Fix it in paraffin, take some slices, and look under a microscope. If you see cells in an orderly arrangement, the obvious conclusion is that it's tissue.So far, I don't see any papers on that. I'd be interested in seeing one.Schweitzer has been quoted:[COLOR="DarkRed"]Whether preservation is strictly morphological and the result of some kind of unknown geochemical replacement process or whether it extends to the subcellular and molecular levels is uncertain.[/COLOR]I found the article from which that was taken. There's more to read on this page:[url]http://tinyurl.com/or488vo[/url[COLOR="DarkRed"]Hendrik Poinar of McMaster University in Hamilton, Ontario, cautions that looks can deceive: Nucleated protozoan cells have been found in 225-million-year-old amber, but geochemical tests revealed that the nuclei had been replaced with resin compounds. Even the resilience of the vessels may be deceptive. Flexible fossils of colonial marine organisms called graptolites have been recovered from 440-million-year-old rocks, but the original material--likely collagen--had not survived.[/COLOR]Science, vol. 307:1852