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.
Imitation Gold is a coating of metal whose color looks like 14k-18k gold, making jewelry more affordable but at the same time keeping the good quality. Imitation gold has a tint of red, and appears to have a reddish yellow hue.