925 Sterling Silver:
925 Sterling Silver is a combination of 92.5% pure silver and 7.5% of another metal, and it is the highest percentage of fine silver possible for jewelry subject to everyday wear. Fine silver (99.9% pure) is generally too soft and malleable for jewelry. Therefore, it is usually combined with copper to give it strength, while at the same time preserving both the ductility and beauty of its original form.
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.