Peridot possesses a rich, glowing velvet luster, and exhibits colors that range from golden tsavorite lime greens to rich emerald grass greens, the latter of which command the highest prices. Peridot is an idiochromatic gem, which means that its color comes from the basic chemical composition of the mineral itself, and is an indispensable element in its make-up. Peridot is colored by ferrous iron that is basic to its composition; the best colors of Peridot generally contain about 10–15% of iron. This runs to the contrary of gems such as ruby or sapphire, which get their coloration from trace elements present as impurities.