Asbestos can be differentiated from rock wool and fiberglass with a jewelers loupe. Man-made fibers are generally uniform in dimension, color, and lustre. When viewed through a loupe these fibers will generally look like shiny, translucent hair, brittle enough to break when bent with tweezers; like glass.
Asbestos fibers, on the other hand, are not individual fibers (like fiberglass) but bundles of fibers that can pulled apart into smaller and smaller bundles of fibers until they are only visible through a microscope. Asbestos is not a glass, but, at the molecular level, a tubular crystalline arrangement of atoms. Through a loupe, asbestos "fibers" will look varied in size from thick as a pencil lead to barely visible wisps.
As others above have noted, it's not likely to be asbestos. However, asbestos is still found in many important applications for which there is no substitute, automobile brake shoes, for one.