Placer deposits are valuable minerals that have been weathered and broken down into sand gravel, and accumulate on river banks or beaches due to their higher specific gravity content. These deposits are the result of gravity separation of minerals carried in rivers or streams, and are produced during sedimentation. Gemstones such as diamonds, rubies, sapphires, chrysoberyls, zircons, tourmalines, spinels, topazes, garnets and other minerals can be washed and extracted from placer deposits.