Opal is a stunningly beautiful and unique gemstone revered for its magical “play of color.” However, as a relatively soft and fragile stone, opal requires special care when tumble polishing. While it is possible to safely tumble certain kinds of opal, lapidarists need to take precautions to avoid damaging these delicate gems.
The key to successfully tumbling opal lies in choosing the right type of opal and using proper equipment and techniques. Softer precious opals and opals with cracks or inclusions should be avoided, as they are prone to scratching, crazing and dulling during the tumbling process. The best options are common opals like hyalite and boulder opal still in its protective matrix. With these resilient forms, getting a smoothly polished opal is achievable with the right know-how.
When preparing to tumble opal, steps must be taken to minimize risks. Only well-shaped, similar sized stones should be used to prevent uneven abrasion. Rotary and vibratory tumblers with smooth, rounded media are gentler than barrel tumblers with coarse grit and rock chips. The opals must also be cushioned in the tumbler and kept wet to prevent cracking. While requiring extra diligence, with the proper materials and techniques, the unique flashing colors of tumble polished opal can be revealed successfully.
What is the opal, and where does it come from
Opal is a hydrated amorphous form of silica, typically containing between three and 21% water by weight. It is classified as a mineraloid rather than a true mineral because of its amorphous (non-crystalline) structure. Opal is widely regarded as a gemstone and has been used in jewelry for centuries.
Opal is found in a variety of locations around the world, including Australia, Brazil, Ethiopia, Honduras, Indonesia, Mexico, and the United States. Due to their vibrant colors, Australian opals are particularly prized and often referred to as “fire opals” due to their vibrant colors.
Opal typically has a vitreous or waxy luster and may be transparent, translucent, or opaque. The most common opal colors are white, gray, yellow, orange, red, green, and blue. However, opals can also be found in many other colors, including brown, black, and even colorless.
Opal is rated a five on the Mohs scale of hardness, which means it can easily be scratched or chipped. However, opal is relatively soft compared to other gemstones, such as diamonds (rated a ten on the Mohs scale).
The different types of opal
There are two main types of opal: precious opal and common opal. Precious opal is the type of opal that is typically used in jewelry, and it can be found in a variety of colors. On the other hand, common opal is usually white or gray in color and is not considered as valuable as precious opal.
Precious opal is divided into three main types: white opal, black opal, and fire opal. White opal is the most common type of precious opal, and it typically has a light background color with darker colored patterns. Black opal is much less common, and its dark background color characterizes it. Finally, fire opal is the rarest and most valuable type of precious opal, distinguished by its vibrant red, orange, or yellow colors.
Common opal is divided into two main types: wood opal and potch. Wood opal is a common opal with a wood-like appearance and is typically brown or black. Potch is the other type of common opal, and it is generally characterized by its duller colors and lack of pattern.
Opal can also be classified according to its body color. Body color refers to the overall color of the stone, regardless of any patterns or markings. The three main body color categories of opal are white, light, and dark. White opals are the most common type of opal and typically have a pale background color. Light opals have a slightly darker background color than white opals, while dark opals have the darkest colors.
Finally, opal can also be classified according to its play of color. Play-of-color refers to the colors seen when the stone is moved in the light. The three main types of play-of-color are single, double, and triple. Single opals have one color seen when the stone is rolled, while double opals have two colors. Triple opals are the rarest, and they have three colors.
Finding Quality Opal Rough
When selecting rough opal for tumbling, you’ll want to look for stones that show good flash – the play of color that makes opal so prized. Check that the opal has vibrant flashes rather than dull or murky tones. Boulder opal still in matrix or ironstone can be ideal, as the surrounding material protects the softer opal.
Another option is opal doublets – thin slices of opal bonded to a dark backing like agate. This shows off the opal’s flash against a contrasting base. Matrix and doublets allow you to tumble thinner, fragile opal that you would think too soft on its own.
For precious opal, look for a bright white or light yellow base to best display flashes of green, red, blue and more. Darker potch opal lacks that lively play of color. Expect to pay $50-100 per gram for quality precious opal mine rough suitable for tumbling.
In terms of size, 6mm to 12mm stones work well. Larger than 12mm and abrasion happens unevenly. Smaller than 6mm and you lose too much material. With the right raw rough, you’ll be ready to tumble!
How to select opals for tumbling
When selecting opals for tumbling, it is essential to choose stones of a similar size and shape. This will help ensure that the rocks fall evenly and not get stuck in the tumbler. It is also a good idea to select opals with a smooth surface, as this will help prevent them from getting scratched during the tumbling process.
Preparing opals for the tumbler
Once you have selected the opals you want to tumble, it is time to prepare them for tumbling:
- You must clean the opals to remove any dirt or debris.
- You will need to sand the opals to smooth out any rough edges.
- You will need to soak the opals in water for at least an hour before tumbling.
Tumbling opal gemstones
After the opals have been prepared, it is time to start tumbling. First, you will need to add the opals to the tumbler along with some medium grit. Next, you will need to add water to the tumbler and turn it on. Depending on the desired results, the tumbling process can take anywhere from a few hours to a few days.
Once the opals have been tumble-polished, it is time to remove them from the tumbler. First, you will need to empty the tumbler and rinse the opals in water. Finally, you will need to dry the opals with a soft cloth.
Polishing opals with different finishes
After the opals have been tumble-polished, you may want to polish them with a different finish. The three most common finishes are high gloss, satin, and matte. High gloss is the shiniest finish and is typically used for jewelry. Satin is a less glossy finish and is often used for display pieces. Finally, matte is the minor polished finish typically used for cabochons.
Tips for tumble polishing opals
Here are a few tips to help you get the best results when tumble polishing opals:
- Start with medium grit and gradually move to finer grits.
- Add water to the tumbler regularly to prevent the opals from getting too dry.
- If using a rotary tumbler, add a small amount of oil to the opals to prevent them from getting scratched.
- Be sure to regularly remove the opals from the tumbler to check on their progress.
- If you are unhappy with the results, you can always start over with a different grit or finish.
- Start with inexpensive materials. If you are new to tumble polishing, starting with inexpensive opals is a good idea. This way, you can experiment without breaking the bank.
- Have patience. Tumble polishing takes time, so be patient and don’t expect overnight results.
Purchasing and Handling Opal Rough for Tumbling
Opal rough is a term used to refer to opal in its natural state, before it has been cut and polished. For lapidary enthusiasts, buying opal rough can be an exciting process. Whether it’s boulder opal, found mostly encased in ironstone, or precious opal, the vibrant ‘play-of-color’ can be fascinating to work with.
Now, where can one get the opals, particularly the rough ones, for tumbling? If you’re looking for opal rough rocks used specifically for rock tumbling, several online platforms cater to your needs. A popular marketplace is amazon.com, where you can find a diverse variety of opal rough suitable for tumbling and polishing. The Aussie Lapidary Forum is another good source, often providing access to individual sellers who offer high-quality rough stones, including precious opals and boulder opals, which are the ones Aussies are particularly proud of. You might find their advice on handling the cutter, cabbing, and tumbling mix rough particularly helpful.
Here are some pointers to remember when dealing with opal rough:
- Always examine opal rough under proper lighting to accurately judge the quality and potential of the stone.
- Never forget that opal varies in hardness and stability, so handle with care to avoid damaging the precious gem.
- While tumbling, monitor the opal frequently to ensure it doesn’t lose too much of its valuable carat weight.
Always keep in mind that patience is key in this process. Take too much off, and you risk losing the valuable color “flash.” On the other hand, leaving the opal too lumpy might not achieve the desired result.
Choosing Opals and Other Rocks for Tumbling
Rocks used for rock tumblers are often chosen based on their hardness, durability, and color. The tumble mix rough ideally includes rocks that are of similar hardness to avoid the softer stones from getting overly worn. While opal rocks are an excellent choice for tumbling, there are also other rocks for tumbling you might consider to create a varied collection.
Here’s a quick table to give you an overview of some additional stones you might consider, and their associated metaphysical properties, which are often why healing stones are sought after:
| Stone | Metaphysical Properties |
|---|---|
| Rose Quartz | Encourages love, heals heart chakra |
| Amethyst | Calming, promotes balance and peace |
| Amazonite | Enhances communication, soothes emotional trauma |
| Girasol Opal | Enhances creativity, aids in relaxation |
| Honey Opal | Boosts self-esteem, improves decision-making |
Whether you are into the metaphysical properties of these stones or just appreciate their beauty, they can make your tumbling and polishing sessions much more varied and enjoyable.
Remember that after tumbling, some of these stones can be made into beautiful beads for jewelry, cushion, or semi-precious stone pieces. Some can be used as specimens for collection or as calming healing crystals. Pink opal rough, for instance, has a soothing effect on the emotional body and is a powerful stone for healing the emotions.
If you’re interested in getting more involved in the lapidary community, consider joining forums and online groups to connect with others who share your interest. For beginners, hope that helps, and happy tumbling!
Tips for Tumbling and Polishing Your Stones
After your rough rocks are ready for rock tumbling, it’s time to prepare your rock tumblers and rock polishers. Here are some tips:
- Use plastic pellets as a filler in your rock tumbler. They cushion the stones and prevent them from knocking against each other too hard.
- Begin with a 220 grit for initial shaping, and then move to a finer grit for polishing. Cerium oxide is a popular choice for the final polish.
- If you want to make cabochons (“cabs” for short) or similar handmade gem items, remember to dop the stone, or attach it to a stick for better handling.
- Always keep your equipment clean. An unclean tumbler would carry remnants of previous grit, leading to scratches on the new batch of stones.
Remember, the beauty of tumbling is in its simplicity. It doesn’t require expensive equipment or materials, just patience, and passion. Enjoy the process, and be amazed at the beautiful pieces you create!
FAQ
Can all opals be tumble polished?
No, not all opals can be tumble polished. Opals that are too soft or fragile will not withstand the tumbling process. In addition, some opals may have inclusions that can be damaged by tumbling.
How long does it take to tumble polish an opal?
The time it takes to tumble polish an opal depends on the desired results. Tumbling can take anywhere from a few hours to a few days.
What is the best grit to use for tumble polishing opals?
The best grit for tumble polishing opals depends on the desired results. You will need to use a finer grit for a high gloss finish. For a satin finish, you can use a medium grit. And for a matte finish, you can use a coarse grit.
Do I need to polish my opals after tumbling?
No, you do not need to polish your opals after tumbling. However, if you want a different finish, you can always polish them with an extra grit or finish.
Can I tumble polishing multiple opals at the same time?
Yes, you can tumble polishing multiple opals simultaneously. Just be sure to add enough grit and water to cover all the opals.
Conclusions
Polishing opals can be a fun and rewarding experience, but it is crucial to understand the basics before getting started. More importantly, remember to take your time and experiment with different grits and finishes to find what works best for you. With a bit of practice, you’ll be able to create beautifully polished opal gemstones that shine like stars. Have you tried polishing opals yourself? What tips do you have to share?
Thanks for the info
I will put rough opal in matrix with 220 to round them out.
You’re very welcome! It’s great to hear that you found the information helpful. Putting rough opal in matrix with 220 grit is a good starting point to round them out. Just remember to take it slow and steady when tumbling opal, as it’s a delicate gemstone that can easily crack or chip if you’re not careful. Good luck with your tumbling and feel free to reach out if you have any more questions!