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How to Cut & Polish Opals: Follow These 9 Simple Steps

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Lapidary is the art of cutting and polishing precious stones. Natural opal variety gets determined by two characteristics: body tone and transparency and can be opaque, translucent, or transparent, depending on its body color. Correctly cutting and polishing these opals brings beauty and exceptional color flash.

The 9 simple steps:

  • Clean the opal 
  • Cut the opal to a rough shape 
  • Examine and mark the opal 
  • Apply gentle pressure to cuts
  • Reevaluate after each cut 
  • Create the basic shape 
  • Mount the opal on a dop stick
  • Shape to its final pre-polish 
  • Polish on leather with polishing compound

Whether you are on a tight budget or have some money to invest in specialized equipment should not deter you from entering the lapidary art. Below, we will discuss the budget-friendly ways of doing it by hand, or if you can afford a Dremel rotary tool, we will explain how to use it. We recommend investing in a cabbing machine and trim saw for the serious artists among you. Then follow the nine simple steps.

How to Cut & Polish Opals
How to Cut & Polish Opals

If you are interested in checking out the best dremels and dremel accessories for cutting and polishing opals you can find them by clicking here (Amazon link).

Is Opal Hard to Cut

Opal is a hydrated formless silica (SiO2nH2O) shape that occurs in the fissures of practically any low-temperature rock. The most prevalent sources are limonite, sandstone, rhyolite, marl, and basalt. The internal structure of precious opal enables it to refract light.

It can take on a variety of colors depending on the conditions under which it developed, including black, white, crystal, and jelly. Fire opal, hyalite, water opal, hydrophane, and honey opal are other varieties.

The most challenging and time-consuming aspect of working with opals is cutting. Of course, you could go all out and go straight for the color bar, removing everything that is in the way, but that could mean you’re making a colossal mistake and losing a lot of money, as every carat counts. The best techniques and skills developed over time are firm touch but not pressure.

Opal is considered a hard material to work with to get the greatest yield out of a piece. When we say hard, we don’t mean that it is as hard as a rock but rather that it is challenging to carve it to perfection.

Practice with other stones to hone your craft, you need patience and skill, and you will see beautiful artwork in no time.

Cleaning Opals Before Cutting and Polishing

The first thing you need to do before cleaning your opals for cutting is to decide whether they are impermeable (that is, they do not allow liquids to pass through them).

Australian opals are non-porous and waterproof, whereas Ethiopian opals are hydrophane and absorb water and oils. You can use a Dremel tool to remove the excess matrix or rock to clean a hydrophane opal before cutting. 

One of the methods you can use is to place your freshly mined opals (still muddy and full of debris) in a tumbler for two days.

First, add the dirty opals into the tumbler, and then fill the tumbler with about 70% water. After the two days, you will have clean opals and muddy water. Tumling opals to clean sometimes help to get some color out of the opals. 

Cleaning opals with denatured alcohol, also known as methylated spirits, and other chemicals is common, although it is not recommended for hydroplane opals since the solvent will be absorbed.

TIP: Not sure how to clean your rocks before cutting and polishing? Check out the methods on how to clean rocks in the article below:
How to Clean Your Rocks and Minerals: 5 Simple Ideas

How to Cut Opal

How to Cut Opal with a Dremel and by Hand
How to Cut Opal with a Dremel and by Hand

Cabbing machines can perform various tasks, including cutting, trimming, grinding, and polishing. Many individuals buy cabbing equipment because they are required for anyone serious about cutting gems and wanting to make amazing lapidary art and jewelry regardless of skill level. However, they are more expensive than hand tools and other rotary devices such as Dremel.

Cutting opals can be divided into three main categories, depending on the eventual use. 

  • Opals with a higher dome shape or cabochon cut: jewelry such as rings
  • Opals with facets: also used in jewelry, but the different facet cuts create brilliance 
  • Artistic carvings and tribal motifs: animals, faces, and leaves are very popular

Each one of these methods of cutting requires practice and patience. 

After sourcing your raw opal, you need to follow these 9 steps to cut opal on a cabbing machine:

  1. First, clean the natural opal (see the section on how to clean opal).
  2. Use a diamond saw to cut the opal to a rough shape called a rub (you can also use a rotary tool like a Dremel).
  3. Thoroughly examine the opal to find the correct angle to approach the color layer. Mark it with a gem marking pen to guide your cuts.
  4. Switch on the capping machine and start with minor cuts moving from a coarser grinding wheel to a finer grinding wheel. Applying gentle pressure and only do small sections at a time. Be patient, and don’t use too much force.
  5. Reevaluate after each cut to ensure you are still on the color bar and correct your approach angle if needed.
  6. Continue making small cuts till you have the basic shape and form you desire.
  7. Once you’ve nailed down the basic shape, use jewelry wax to mount the opal on a dop stick. You can better manage the final cutting process because you can see the natural opal at a glance with a dop stick. 
  8. With the opal securely fastened on top of the dop stick, shape the stone to its final shape using the highest grit wheel you have. You have finished the pre-polish cut when you’re happy with the final form and can see the beautiful color flash from every angle.
  9. All that is left is to polish the opal on the leather lapidary wheel with a polishing compound.

BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):

Cutting Opal With a Dremel

So, slicing with a Dremel is not ideal; if you have a trim saw, always use it; it’s a lot safer, a lot faster, and it’s simply an all-around better tool to use than the Dremel. That said, it does not mean you could or should not use a Dremel tool for more minor cuts.

Getting the correct cutting bit to cut the opal is essential to get the best result. The diamond-coated metal blade bit is the best for cutting opal when using a Dremel.

Please do not use the black hard abrasive cut-off wheel since it will burn and blacken your opal. Because the blade’s diameter is around an inch, the sintered diamond-coated blades do not cut very deep, yet the actual cutting depth is around a ¼ inch.

Keeping the opal cool with water is also a challenge since the rotating bit blasts the water off quicker than you can add it. If you do not have a dedicated dripping system, you will need to dunk the gem in water after each pass to prevent the opal from overheating and the dust flying everywhere. Remember to use a face shield or some other eye protection.

Use the nova point tips to shape the opal after rough-cutting the edges with the cutting blade. 

Progress through the different grit points to reach your desired shape and pre-polish finish.

  • 280 grit diamond pacific nova points
  • 600 grit diamond pacific nova points
  • 1200 grit diamond pacific nova points
  • 3000 grit diamond pacific nova points

TIP: The best tools for polishing rocks and adding a soft glimmer are the rotary dremels. Check out reviews for the best dremel drills on the market in the article below:
3 Best Dremels for Polishing Rocks & Crystals + Accessories

Cutting Opal By Hand

For opal collectors and lovers who enjoy seeing the color bloom, cutting an opal by hand can be a satisfying activity and well worth the effort.

We suggest getting a good corundum knife sharpening stone to hone the gem when cutting opal by hand. Most corundum knife sharpening stones have a high grid side and a low grid side.

You will find that specific knife sharpening stones work best with water or oil. Use only water stones since some opals are more porous and can absorb the oil and degrade the gem. 

Holding the gemstone firmly between your fingers, pressing down on the wet stone, grind the opal to the desired shape with forwarding and backward motions.

Using water helps with the dust and lets you see the color layers as you hone. After you have honed down the opal to the basic form (called pre-form) you want, you can give your fingers a rest and mount the opal on a dop stick.

Some people use super glue to attach the opal to the dop stick but using jewelry wax may give you a better experience.

The dop stick allows for a better vantage point and control when cutting the opal into its final shape. You will still use the knife sharpening stone to hone the dopped opal to its final form. When satisfied with the profile, you can move to sandpaper to refine the opal. 

Go to the section “Polishing Opals with a Sandpaper” to learn how to finish and polish the opal by hand.

TIP: Opals are among the most beautiful gemstones you can find in nature. Check out the best locations for finding opals in the United States in the article below:
4 Best Locations for Finding Opals Near Me (United States)

How to Polish Opal at Home

How to Polish Opal at Home
How to Polish Opal at Home

In general, aluminum and cerium oxide polishes offer better results than diamond polishes. Many oxide polishes are 0.3 microns or more refined, depending on the manufacturer, resulting in a polish compound that is close to 100,000 grit.

Cutting the opal to 1,200 grit and then polishing it with diamond pre-polish is a standard polish scenario when done by hand or with a Dremel tool. A typical oxide polish scenario involves cutting the opal to a worn 1,200 grit lap and polishing it with cerium or aluminum oxide on the leather lap.

Polishing Opals in a Rock Tumbler

When opals are shaped and polished in a rock tumbler, you may lose almost 20% of the mass and 50% of the color flash.

When you tumble opal in a rock tumbler, you lose control over the shape of the finished piece. The lighter color areas wear away quickly when tumbled, resulting in an irregular rather than a smooth surface 

A rotating tumbler will round any protrusion, edge, or point. Soft sections of the stone will be treated more aggressively than harder areas, with any existing or nascent fractures likely shattering in the tumbler. Every few days, open the barrel of your rotary tumbler to see what’s going on. 

Polishing Opals with A Dremel

Polishing opals with a Dremel is faster than doing it by hand. Using the felt tips with a polishing compound is the way to go. You can progress through the different diamond polish grits available to you.

Examples are 600 grit, 1200 grit, 1800 grit, and 8000 grit. You may find that you go through a fair amount of felt tips while polishing, which can be costly in the long run. 

Making a wooden tip from a dowel stick and rounding it like the nova tips can save you a lot of money.

Attach it to one of the Dremel threaded bars, and you’ll find it lasts a long time and works well with the polishing compounds. Mix the powder compound with water to create a paste and apply it to the opal or Dremel bit. Polish the opal to the desired finish using back and forward motions with the Dremel.

TIP: To make the opal affordable to a wider range of people, a lot of different fakes have been created. Check out the main differences between real and fake opals in the article below:
Real vs. Fake Opal: Focus on These 6 Differences

Polishing Opals with a Sandpaper

Hand polishing an opal without machinery is a fantastic alternative for prospective opal cutters who want to try something new without investing in expensive equipment. Hand polishing opal without a machine is easier than you think; all you need is specific tools and a little sweat equity to unveil the beauty.

You will require the following:

  • 360 grit sandpaper
  • 1000 grit sandpaper
  • 1500 grit sandpaper
  • Towel
  • Water bottle
  • Opal on a dopping stick 
  • Strip of leather
  • Cerium oxide polishing powder

Start with 360 grit sandpaper and place it on a towel on a flat surface and add water to the sandpaper.

The water isn’t there to keep the opal from heating up due to friction, as it would if you were using a machine; it’s there to keep the dust out of your lungs. The sandpaper helps you create a smoother effect on the opal.

Expert tip:

“Try to stay on the same spot of the sandpaper since it will wear out and create a smoother finish on that particular grit.” 

Move on from the 360 grit to 1000 grit and then 1500 grit. With this final grit sandpaper, you’ll be astonished at how close you can get to a polished look. It is unnecessary to use a finer grit than 1500, but you are welcome to experiment and see the kind of result you’ll get.

Now you are done with the sandpaper, and it is time to move on to the best part. Take some of the cerium oxide powder and water, make a smooth paste, and place it on the leather strip.

Start polishing the whole gem with the opal still attached to the dop stick. Rubbing motions on the leather with the cerium oxide creates a beautiful finish. Well done, you cut and polished an opal by hand.

TIP: Rotary rock tumblers – the ones with a drum that turns – are the most common type of tumbler used by lapidary hobbyists. Check out the complete guide on how they work in the article below:
Rotary Rock Tumblers: How They Work & Which One Is Best?

Polishing Opals with Cerium Oxide

Because opals are made up of glass-like material, polishing them with a glass polishing solution is a good idea. The glass polishing compound can readily remove most fine hairline scratches on opals.  

Place the polishing drill bit in the head, then create a slurry with water and Cerium Oxide powder. Apply the compound to the opal to remove hairline scratches on the face after dipping the polishing head into the paste. This buffing process removes the scratches. You’ll need a spray bottle with plenty of water to keep spraying on the opal to keep it cool.

Mix Cerium Powder and water to make a paste-like consistency when polishing by hand. Apply the paste to a leather strip and polish the opal to a fine shine.

Re-apply the compound as needed while spraying the opal and paste with water to keep it moist. Finish by wiping the opal surface well to remove any remaining cerium paste. 

After thoroughly cleaning the opal surface to remove contaminants, we recommended polishing the opal with a machine-operated leather lapidary pad. Make a paste-like consistency with Cerium Powder and water, and apply a thin coating of cerium paste to the lap pad.

Polish the opal by using slight pressure while holding it against the disc. Re-apply water as needed to maintain a wet surface, and if the consistency becomes too watery, add more Cerium Powder.

Conclusion

Whether you’re cutting opal to make magnificent jewelry or creating artistic tribal art, you can achieve the perfect outcome. Machines make the process faster, but you can accomplish the idyllic end by hand.

The old saying that practice makes perfect applies here, and the ideal techniques and talents needed are firm touch but not pressure, which you develop over time.

Whether you use hand tools, rotary tools, or a cabbing machine, cutting the opal to the desired shape should be reasonably simple. By hand or machine polishing the opal using Oxides or Diamond Pastes, the ultimate result should be an outstanding opal with excellent color flare.

TIP: Opal is a one-of-a-kind, highly valuable gemstone. Find out the key factors that determine opal’s value in the article below:
8 Factors Why Opal is Valuable (Prices for Different Types)