Opal Polishing 101: Tips, Techniques, and Common Mistakes

Cutting and Shaping

Using the Trim Saw

Carefully slice the rough opal to remove excess material and isolate the desired section containing the color bar.

Grinding with Diamond Wheels

Progress through the following grit sizes:

• 80-220 Grit: Shape the opal, removing significant imperfections.
• 280-600 Grit: Refine the shape and smooth the surface.
• 1200-3000 Grit: Pre-polish the opal, preparing it for the final polish.

Always use water to cool the stone and prevent overheating. Good preparation in the earlier stages of cutting an opal will result in a very short time needed for final polishing. There is a misconception with a lot of cutters that they need to focus mostly on the final polish rather than the preparation stages leading up to it.

Dopping the Opal

Dopping involves attaching the opal to a stick for better control during polishing

• Select Appropriate Dop Sticks: Use wooden dowels or skewers, ensuring they are of consistent length and thickness.
• Apply Dop Wax: Heat the wax, usually with a candle, and apply it to the dop stick, then press the opal onto the wax, ensuring it is securely attached.
• Allow to Set: Let the wax cool and harden before proceeding.

Polishing the Opal

The final polish brings out the opal’s brilliance:

• Use Polishing Compounds: Apply cerium oxide or diamond paste to a leather or felt pad. Different people prefer different compounds; and it really depends what type of opal or job your doing as to which you will use also.
• Polish Gently: Work in a circular motion, applying light pressure to avoid damaging the stone. Polishing opals rely on a good sense of feeling.
• Inspect Regularly: Check the opal frequently to monitor progress and prevent over polishing.

Utilizing a Dremel Tool

A Dremel tool is useful for detailed work and carving:

• Select Appropriate Bits: Use diamond-coated bits suitable for opal.
• Work Slowly: Operate at low speeds to maintain control and prevent heat buildup.
• Cool Frequently: Dip the opal in water regularly to keep it cool.

This method is especially beneficial for intricate designs and small scale projects.

Differences in Cutting Boulder vs. Lightning Ridge Opals

Boulder Opals

• Ironstone Matrix: Boulder opals are attached to an ironstone backing, which adds durability but requires careful polishing to avoid damaging the opal layer.
• Cutting Approach: Often cut in freeform shapes to follow the natural contours of the opal within the matrix.
• Prepare to get Dirty: Due to the nature of boulder opals, prepare to get covered in ground brown ironstone and sandstone. It is not a clean gemstone to cut.

Lightning Ridge Opals

• Black Opals: Known for their dark body tone, which enhances the play-of-color. There are two types of opals from this region; seam opals and nobby opals. As an opal cutter it is important to know the difference, as each of these types of opals should be approached differently when cutting.
• Cutting Approach: Typically cut into standard shapes like ovals or teardrops, focusing on maximizing the color bar.

Understanding these differences ensures appropriate techniques are applied for each opal type.

Safety Considerations

Always prioritize safety:

• Wear Protective Gear: Use safety glasses and a dust mask to protect against debris and inhalation of fine particles.
• Maintain Equipment: Regularly check and maintain tools to ensure they are in good working condition.
• Work in a Well-Ventilated Area: Ensure adequate airflow to disperse dust and fumes.

Common Mistakes One of the most common mistakes people make when polishing opals is using too much pressure or speed, which can easily crack or chip the stone due to its relatively low hardness and internal water content. Another frequent error is skipping grits; jumping from a coarse diamond wheel directly to a polish without adequately smoothing out the surface leads to a dull, uneven finish full of microscopic scratches. Many beginners also neglect to keep the opal and the polishing tool consistently wet, which results in friction induced heat that can cause crazing or even breakage. Using the wrong polishing compound, like metal based polishes or harsh abrasives, can damage the opal’s surface permanently. Lastly, some attempt to polish doublets or triplets (composite stones) as if they’re solid opals, unknowingly damaging the glue layer or plastic cap. Proper technique, patience, and knowing what type of opal you’re working with are essential to avoid costly mistakes. By following these steps and understanding the unique properties of different Australian opals, you can effectively cut and polish these gemstones to reveal their natural beauty.

Frequently Asked Questions about Opal Cutting and Polishing (FAQ)

Can You Repolish an Opal?

Yes, opals can absolutely be repolished, in fact, polishing is one of the final and most crucial steps in bringing out an opal’s true beauty. Whether it’s a rough stone or a dull old gem, polishing restores brilliance and enhances the play-of-color.

There are two scenarios:

• Professional polishing (done with diamond wheels and cerium oxide on felt or leather pads)
• Light home polishing (for maintenance or mild restoration)

If your opal is scratched, matte, or dull, polishing can often bring it back to life, as long as there’s enough material left to work with. Be cautious with thin or doublet opals, as over-polishing can remove layers.

How do I polish an opal?

Polishing opals involves shaping the stone with progressively finer abrasives and finishing with a polishing compound like cerium oxide on a felt or leather wheel. Keeping the stone cool and wet is essential to prevent damage.

Can I polish opals at home?

Yes, with the right tools such as a Dremel, dop sticks, polishing compounds, and safety gear, you can polish opals at home. Beginners often start with inexpensive rough opal to practice.

What tools are needed to polish opals?

• A rotary tool (like a Dremel) or lapidary machine
• Diamond grinding wheels or sanding attachments
• Felt or leather polishing pads
• Polishing compounds (e.g., cerium oxide)
• Dop sticks and wax
• Water for cooling
• Safety equipment (glasses, mask)

How to Make Opals Sparkle Again

If your opal has lost its luster or looks dull/cloudy, here’s how to revive it:

For Light Maintenance:

• Use a soft damp microfiber cloth to remove dirt and oils.
• Gently buff with a clean, dry cloth; this alone can bring back some shine.
• If that doesn’t work, apply a bit of cerium oxide polish or diamond paste using a felt pad or soft leather and rub in circular motions by hand.

For Professional-Level Sparkle:

• Use a 600-1200 grit diamond wheel to pre-polish, then move to 3000 grit or a felt pad with cerium oxide for the final shine.
• Always use water as coolant to avoid heat cracks.
• Avoid aggressive pressure as opal is fragile and can chip.

Note: Never tumble polish precious opals. The vibration and pressure are too harsh for their structure.

What Is the Best Polishing Compound for Opal?

The top recommended compounds for opal are:

• Cerium Oxide: The industry gold standard. Produces a high gloss, glassy finish. Best applied on a leather or felt pad with water.
• Tin Oxide: Sometimes used, but slightly less effective than cerium oxide for opals.
• Diamond Paste (8000–50,000 grit): Used for very fine polishing, especially for crystal opals or perfectionists. Also often used to polish the backs of opals.

Tip: Use minimal compound; too much creates drag and reduces effectiveness. Let the friction and finesse do the work.

How often should I polish my opal jewelry?

Polishing should be done sparingly to avoid unnecessary wear. Generally, polishing once every few years or as needed to maintain the shine is sufficient. Always use gentle methods to polish an opal ring safely.

How Do I Fix My Cloudy Opal?

A cloudy or milky opal can result from:

• Surface residue (dirt, oils, soaps)
• Micro-scratches or abrasion
• Absorption of moisture (especially with hydrophane opals like Ethiopian opals)

How to Fix:

Clean the surface:

• Use warm water and mild dish soap.
• Gently scrub with a very soft toothbrush.

Buff with a microfiber cloth:

• Often this alone removes the “fog” from oils and fingerprints.

Polish:

• For stubborn cloudiness, polish lightly with cerium oxide and felt or leather pad.
• Avoid heat or chemicals as opals are sensitive.

If your opal has turned permanently milky, it could be a hydration issue or internal damage, especially with low quality or treated stones.

How to Revive a Dull Opal

Dull opals can often be restored with the right polishing process.

Clean the stone with water and mild soap.

Inspect for scratches; if the surface is intact, a light polish will work.

Hand Polish:

• Use cerium oxide and a soft felt or leather cloth.
• Buff gently in circles for a few minutes

Machine Polish:

• Use a felt polishing wheel and cerium oxide.
• Keep the stone wet and cool at all times.

Can I Polish Opal with Toothpaste?

Technically, yes, but with caution and only for very light polishing or cleaning.

Here’s the reality:

• Toothpaste is mildly abrasive, so it can remove surface grime and a tiny layer of material.
• Use only non gel, plain white toothpaste (no whitening agents or baking soda).
• Use a soft cloth, apply a small amount of toothpaste, and rub gently in a circular motion.
• Rinse thoroughly and dry.

Don’t use toothpaste on high value opals, doublets, or boulder opals; it’s too unpredictable and not precise enough for fine polishing.

Can I use commercial jewelry cleaners on opals?

No, many commercial cleaners contain harsh chemicals that can damage opals. Stick to mild soap and water for cleaning.

How should I store opals to maintain their polish?

Store opals in a soft, padded jewelry box away from direct sunlight and heat sources. If possible, store them separately from other jewelry pieces to prevent scratches.

What are common mistakes to avoid when polishing opals?

• Using excessive pressure or speed, leading to overheating
• Skipping grit stages, resulting in scratches
• Neglecting to keep the stone wet during polishing
• Not inspecting the stone under good lighting between stages

Is tumble polishing suitable for opals?

Tumble Polishing is generally not recommended for opals, especially precious opals, as it can lead to uneven surfaces and loss of material. Hand polishing allows for better control and results.

Are ultrasonic cleaners suitable for cleaning opal jewelry?

Ultrasonic cleaners may be a good way to clean built up sweat and dirt in crevices of a ring or its small diamonds. Using an ultrasonic cleaner with a set opal however may (although highly unlikely) de-stabilise the opal and cause it to crack. Remember that opals are natural stones; made up of potch and sometimes sand. The ultrasonic may de-stabilise any materials within the opal. It probably won’t happen, however we don’t recommend using this method just in case. Use at your own risk!

Looking for Rough Opal to Cut? Make sure to check out our current Rough Opal Parcels Available.