Opal is a gemstone that doesn't need any particular care, just the normal care you would use with any other gemstone. However, if you wish to clean your opal, you should follow some simple instruction. Put the opal in a bowl contained water at room temperature. Do not add any chemical or detergent. Simply use a brush (e.g. toothbrush) with soft bristles or soft nylon and gently wipe the surface of the opal. This process removes the dust from the opal. Once cleaned, dry the gemstone with a soft cloth (possibly a microfiber cloth). At the end of the process, your opal will regain the original brightness. By using this sample and effective method you will be able to enjoy the endless natural beauty of your gemstone.
Do not use abrasive substance, polishing substances or creams, glycerine, acid detergents or alkaline detergents. All above listed substances damage the opal structure. If you ask your jeweller to clean your opal, remind him not to use any ultrasound wash. Ultrasound washing would damage the surface of your gemstone.
Just some recommendations.
Never leave your opal on the dashboard of your car in the sunlight in the middle of summer. Never take gemstone from a very hot place to a very cold place. The termal shok could in fact compromise the stability of the gemstone. The opal is made up of a high percentage of water. The thermal shok could cause the dehydration or expansion of the molecules of water: this could in the end damage the stability of the gemstone. The best way to take care of your opal would be wearing it as much as you can. The simple act of wearing it in fact will preserve the natural brightness and vividness of the colours. Why is that? It's easy. As we just mentioned, since the gemstone is partly composed by water, it absorbs the humidity and the heat of the human body from the sweat and the transpiration of your skin. Humidity and heat preserve the opal's natural balance.
So we'll say it again: THE BEST WAY TO TAKE CARE OF YOUR OPAL IS TO WEAR IT AS MUCH AS YOU CAN!