Gemstone: A material possessing beauty, rarity and durability (and acceptability). e.g. diamond, ruby, emerald. Ornamentals: A class of gemstones generally more common and found in large sizes often used on a larger scale such as carvings, furniture or mass produced jewellery. e.g. Lapis lazuli, labradorite, malachite. Natural Gem: Gem material which has been mined/collected from a natural source. Synthetic: Gemstones produced under laboratory or industrial conditions from the same chemical ingredients as the natural gems and having the same major properties as their natural counterparts. e.g. Verneuil ruby, Verneuil spinel, CVD diamond. Treated: Treating or manipulating a stone to change its appearance. Treatment can be applied to both natural and synthetic gem material. e.g. heat treatment, irradiation, glass filling. Imitation: Stones, either natural or synthetic, which imitate in appearance a more valuable stone. e.g. glass, synthetic moissanite, cubic zirconia.