Onyx is a banded variety of the oxide mineral chalcedony. The colors of its bands range from white to almost every color (with the exception of some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white.
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.