Choosing An Opal for Hand Made Jewelry
One is the nature of the stone itself. I'm not aware of any other stone with as much variety in the way it presents from one stone to the next.
Opals can look any of a seemingly infinite number of ways.
Some may present with a dark background speckled with numerous tiny pinpoints of contrasting color, dots of bright green and red on a field of purple or indigo. It's unusual shape set things up perfectly for me to do what I do best. In other cases, the flex of color could be more significant, known as a harlequin opal.
Others may be entirely monochromatic fields of vibrant royal blue with subtle bands of color, giving the effect of gazing into a deep ocean from a altitude.
Some stones have many matrices, or mother stone, included in the piece in such a way as to create a dramatic effect. These matrices can appear as a mosaic of little petitions, with dots or shapes of color inside each small cell. Other times, it could provide a heavy dark frame around the spectacularly brilliant pool of light.
Then there are the black opals; dark, mysterious, as deep as the ocean with spectacular flashes of color concealed within that come rolling to the surface like mythological phantoms of light in hues of greens pinks and reds, they vanish again with the movement of the stone. Wow!
Some things to consider about opal if you are contemplating acquiring a piece of opal jewelry.
Stones are rated for both hardness and toughness. For hardness, opal rates (depending on the source) between a 6 and 7 or7 1/2 on a scale to 10, which is not bad actually, comparable with most other crystals that are commonly found in rings and other jewelry. The issue with opal lies in its toughness rating, which is poor. It's characteristic and overall durability can vary wildly from stone to stone, but it's generally safe to assume that an opal can be quite brittle and susceptible to contact shock. Things like accidentally smacking your opal on the edge of a car door, or dropping it on a tile floor can chip or crack a stone and pose the most significant hazards to your opal.
Beyond impact shock, much has been written about the sensitivity of opals to temperature and chemicals. Again, there will be a lot of variance from stone to stone about this, but as a general rule, I usually advise people to remove their opal jewelry if they're going to be spending time and pools or hot tubs, for exposing it to any harsh cleaning detergents or chemicals. After 30 years in the business and having worked with many opals, I have yet to hear a client comment on having seen damage from this, but better safe than sorry...
Storing your Opals
Regarding storage, I've read of people storing their opals in water. Given that the water is pure of chemicals like chlorine, I don't see the harm in this. I've asked my opal dealers about it, who inventory thousands of stones, and they laugh at the notion. One explained to me that when the rough is brought up from the mines, it's left in the hot sun of the Australian outback for about two years before it's cut up into pieces. This is done to allow the stone to stabilize to avoid any unexpected changes down the track. As with the chemicals, the likelihood of your opal changing due to extremes in the heat is in my experience remote, but again, better safe than sorry. Best not to leave it in extended periods in somewhere that might get hot like indirect hot sunlight with poor air circulation, in a pocket of clothing in the dryer, that kind of thing. My rule of thumb is that anything that would be uncomfortable for you is probably not good for your opal.
In short, opal is an exceptionally beautiful stone that's been used in jewelry for centuries. It does have its limitations, and these should be honestly considered as part of your decision, particularly if a ring is something you are contemplating.
If you're not accustomed to wearing opals, you will have to cultivate the automatic intuition required for your piece's longevity. Simple precautions like removing it before doing yard work or going to the gym or into the pool can help ensure a healthy life for your stone but can require a bit of time and effort to cultivate these habits.