What does 825 fas on a gold and diamond ring mean?

The marking "825" on a gold and diamond ring indicates that the metal is composed of 82.5% pure gold, which is equivalent to 20 karats (the remaining 17.5% is typically made up of other metals such as silver or copper). This marking signifies the quality and purity of the gold used in the ring. It's important to note that the presence of diamonds does not affect the gold content but may contribute to the overall value of the ring. Always verify such markings with a professional jeweler for authenticity.