Although jade is mostly known for its imperial green variety, the term jade is actually an umbrella term that encompasses a variety of gemstones. The only two pure forms of jade are nephrite and jadeite, with jadeite being the rarer and more valuable of the two. Recently, other varieties of gemstones with mixed composition have also been traded and marketed as jade, including omphacite, jade-albite and chloromelanite. Jade is famed for its green color and greasy luster. In many cultures, green jade is considered precious and sometimes it is even considered to be more valuable than gold. Although the most desirable color is green, jade gemstones can also be found in various shades of white, gray, lavender, orange and other colors. Burmese imperial jadeite is the most valuable and desirable jade, and it is also one of the rarest of all colored gemstones.