If you are science minded and love natural fibers the IYNF2009 just released a series of photomicrographs of 18 natural fibers. Facinating to see the scales on wool and the lack of scales on angora or flax.
Did you know that angora fiber from the angora rabbit is 11 to 13 microns in diameter, alpaca is 20 to 70 microns, cashmere is 14 to 19 microns, linen is 12 to 16 microns, kid mohair is 23 microns, adult mohair up to 38 microns, silk is 10 to 13 microns -- on a par with angora, while wool is 16 to 40 microns -- 16 being the finest merino from specially fed and housed sheep. Average merino fiber diameter is 22 to 24 microns.
Why does it matter? Fiber diameter is directly related to softness and comfort next to the skin. The finer diameter the fiber the softer it is. Angora rabbit is the finest diameter fiber, with the exception of quiviut which weighs in at 10 microns and is plucked from the musk ox in the north.
But angora rabbits can be kept as pets and so their fiber is accessible to every fiberista, while the musk ox is exclusive to Alaska and the North of Canada.