These somewhat fragile but so lovely gems are unique among the gemstones. I have taken rough material, cut and polished many opals. I cannot count the number of opal stones I have set into jewelry. I do love opals.
Opal advice. Here are the main things to think about when wearing and storing opal jewelry. First of all, opal is not as strong as some other stones but certainly is as durable as most emeralds you see. Opal is not as hard as emeralds but most emeralds will chip easily an due to internal flaws may even be damaged by cleaning! Opal is pretty safe when cleaned properly and is not going to chip or break unless it is give an nasty knock. You do have to be careful not to let the stone run against hard things or knock it around. Then again, who wants to knock around any jewelry!
Opal is a "glass-like" material, very similar to glass with a few particular exceptions: The glass-like structure explains the ability of opal to chip or scratch. Think of opal as glass and you will take good care of it automatically. Then again, although made of the same silica material as glass, opal is quiet different and that difference is what makes this precious stone so wonderful. Imagine taking a bunch of glass marbles and put those into a cereal bowl. Fill the bowl with water just enough to cover the marbles.
This is a simple visual example of how opal is constructed inside the gem. Over time, small spheres (balls) of silica come together and layer together until a complete stone is formed. Between the microscopic beads of silica is some water. Of course, the beads or balls of silica in an opal are much more tightly together than in the "marbles in a bowl" example and the water is much less. Opals may contain up to about 10% water.
The color and fire of an opal comes from the groups of the silica balls. The very size of the balls determines what light is reflected back to the eye. Some groups are close enough to reflect red light while others spaced a bit differently will reflect blue or green light. The balls break up the light and reflect a certain color depending on the size of the silica balls and the spacing of the balls in the gemstone.This is where the color comes from.
The water in an opal is stable, in a stable opal! Some opals are so "water logged" when mined that is a few weeks in dry air the stone will crack from drying out! Gem quality opals do not do this. Opal chosen for cutting into stones have a water content which is contained in the stone and are proven to be stable and safe. These opals should not change from "water loss" over the lifetime of the jewelry. Soaking an opal in water or oil is not needed and comes from old rumors.
General Care. Here is the rest of the care information. First of all, think of the opal as glass, even thought is it not glass but is similar. Keeping this in mind will prevent damage. Cleaning is easily done with a mild dish detergent at room temperature. Use a very soft brush or your fingers to take body oils and soil off the jewelry.Rinse and pat dry. This is an excellent time to check and be sure the stone is secure and tight in the setting. Tap the ring next to your ear to hear a slight "rattle" indicating a loose stone.
Heat and cold may damage an opal. Generally, when very sudden and extreme changes of temperature happen, an opal might be damaged. This is like heating the stone quickly with a flame..zap, like most other stones it will break. Everyday changes in temp will be safe. Do take care in extreme cases like going from a sauna to a dip in a frozen pond! That kind of temperature change could damage the stone. Everyday wear is safe.
I would not jump into a hot shower when coming in from the cold while wearing opals. Simply take the ring off and keep it out of the bath in the first place. This keeps the stone cleaner by avoiding very difficult to clean "soap scum" and the potentially dangerous sudden heat change.
Avoid abrasives. Abrasives are like sandpaper. Things which will scratch glass will scratch an opal. Take the ring off if you are going too wash dishes, working in the yard and when filling a sand box or applying makeup. Yes, makeup is abrasive. Most of the dark smudges folks get from wearing necklaces comes from makeup. The very fine particles in the make up are like microscopic sandpaper, rubbing away gold so fine that the gold looks black. That is the cause of most jewelry smudges, gold rubbed away by the finea "sandpaper" effect of make up.
Opal can be scratched by makeup. The scratches will be so fine you will not notice but will eventually take the shine off of the stone. Please put opals and any and all jewelry on after any make up, hair spray or other things ladies use are finished. Store the jewelry where it will not bounce into or rub against other jewelry. That is about as safe as you can get.