Did you know that October birthstones are opal and tourmaline? These gemstones have a colorful backstory. Opals are made of silica gel, which is the result of water being trapped in cracks within the rock. Tourmalines come from an aluminum-magnesium borosilicate mineral with trace amounts of iron, chromium, manganese, copper or nickel. While these stones don't have much in common on their own they do share two things: they have a colorful backstory and are both beautiful.