Chlorine bleach, a common household liquid, can pit gold alloys, as can prolonged exposure to chlorinated water. Customers who swim a lot in chlorinated pools should be aware of this. If an alloy becomes pitted, it weakens, making gemstone loss possible.
Diamonds are very hard but they’re not indestructible. Sometimes, people wear two rings on the same finger, as in the case of a wedding set. When that happens, one can move or turn slightly and scratch the other. It’s bad enough when they’re both diamonds, but a diamonds can do a lot of damage to a softer colored stone. One possible solution to this is to solder the two rings together so they can’t move independently. Loosened diamonds can also scratch and damage jewelry metals.
During normal wear, earrings, pendants, and necklaces are less susceptible to damage than rings, bracelets, and bangles.