Some years ago, a product tradenamed "Franklin Fiber" was produced by USG Industrial Products. Franklin Fiber was described as "a calcium sulfate micro-fiber" and was produced at US Gypsum's East Chicageo, Indiana plant. It was discontinued in the late '90s.
It was a very short fiber (so short, in fact, I described it as having only one end) - about 50-60 microns, with a diameter of about 2 microns. It had a profound effect on improving the tensile and flexural strengths of molded friction material composites.
Is anyone aware of a similar product being available?