Jadeite is classed as a pyroxene and is a silicate of sodium and aluminum. It is a cryptocrystalline mineral and its minute crystals are interlocked to form a compact aggregate. It ranks 6.75 or 7 on the Moh scale of hardness. Chinese lapidaries do not appear to have worked with jadeite on a regular basis until the Qing dynasty. Most of the jadeite used in China came from the region around Tawmaw in Upper Burma. While both nephrite and jadeite are found in a range of different colors, depending the presence of small quantities of iron, chromium or magnesium, the brilliant green stones used in fine Chinese jewelry are jadeite.