October Gems is a term used to describe opals, which are precious gemstones that come in a variety of colors and shapes. Opals are composed of silica and water, and they are known for their unique play of color, which is caused by the diffraction of light through the stone's microstructure. Opals are found in many countries around the world, but Australia is the largest producer of opals. They have been prized for centuries for their beauty and rarity, and they are often given as gifts to celebrate special occasions.