Space Shuttle Tile

Years ago, NASA gave away space shuttle tiles to educational institutions for demonstration purposes. One thing that amazed me when I first picked one up is how lightweight

it was - but I guess that makes sense if they needed to be launched into space. We still use them as props at outreach events.  I have included an optical micrograph of the glass fibers in the tile structure.  The black marks at the bottom of the picture are one millimeter apart.