Composition shingles are made of organic felt manufactured from wood and paper fibers. Fiberglass-base shingles are made of manmade fiberglass mat. Both kinds are soaked in asphalt, but the fiberglass base shingles are more fire-resistant than the organic ones. Asphalt shingles have mineral granules embedded in them; when you find these granules washing away, it's a sign that you need to repair or replace your shingles