Natural stones (stones that can be used in jewelry after cutting and polishing) are well-known for their vibrant colors, but are not one of the four precious stones (diamond, emerald, ruby, sapphire).
Jade is an ornamental rock. The term jade is applied to two different metamorphic rocks that are composed of different silicate minerals: nephrite and jadeite. Nephrite and jadeite were used from prehistoric periods for hardstone carving. Jadeite has about the same hardness as quartz. Nephrite is slightly softer, but is tougher (more resistant to breakage) than jadeite.