Just a reminder that different materials have different volume expansion coefficients, which means that metal will expand/shrink differently than MOP/onyx/carnelian when temperature and humidity changes. In extreme cases, the inserts may fall off due to this particular reason. Water is not a major concern to metal, but soap and other chemicals can dull your platinum, leave a film over diamonds and wear off your rhodium plating on your WG. Water, soap and chemicals can also alter the appearances of your stones and MOP in the long run. VCA is very clear that you should avoid water when wearing MOP, and diamond is the only gemstone that they recommend cleaning with water.