Glass is fashioned from a mixture of sodium silicate, calcium silicate and silicon dioxide. Colored glass is made by adding specific metal ions or minerals to the molten glass while it is being formulated. Metals are transition elements and show characteristic colored compounds. Glass can be used to create look-alike, or simulated, gemstones for jewelry, taking on the color of any genuine translucent or transparent stone.
Glass is rated at 5.5 to 6.5 on the Mohs scale of hardness. It can be brittle, so it is generally set in a durable metal. Glass beads are an extremely popular jewelry item, and oftentimes small simulated stones are used in birthstone jewelry items.