How To Cut And Polish Opal Like A Pro!

by Jason Blaiklock

Opals have captured the hearts of gemstone enthusiasts worldwide. Behind the scenes of opal markets, there is a crucial process that brings these captivating gemstones to life: opal cutting. This intricate art form demands skill, precision, and a profound understanding of the opal's distinct characteristics.

Graeme Blaiklock, the founder of Australian Opal Cutters, has been perfecting this craft for over 50 years. In this guide, Graeme shares his unique opal cutting and polishing techniques and tips with you.

Step 1: Hand Pick Your Opals

The journey of opal cutting begins with the selection of the finest quality rough stones. Australian opal mines are renowned for producing some of the world's best opals, and places like Lightning Ridge, Coober Pedy, and Andamooka are popular sources for high-quality gems. Once the rough stone is obtained, the cutter meticulously evaluates its shape, size, and any inclusions or cracks that might affect the final product.

Begin by hand-picking multiple opals ready for cutting. Ensure the ironstones are solid and crack-free. For new opal cutters, starting with reasonably low-grade materials is a good idea. These may not yield beautiful stones but will help you build confidence and develop systematic opal cutting and polishing skills. As you gain confidence, you can challenge yourself with higher-grade opals.

Video 1 How to Cut Opal from Australian Opal Cutters on Vimeo.

 

Step 2: Study the Opal

Next, the cutter must determine the optimal approach to cutting the stone, aiming to showcase its unique beauty. This involves making a series of precise cuts that reveal the opal's captivating colour play and intricate patterns. In some cases, cutters may choose to leave some rough sections intact, enhancing the stone's natural charm and character.

When you have an opal in hand, look for the colour first. Identify the 'seam' or 'flat line' of colour within the gemstone and decide which side is the 'top.' Use a good Halogen light source or sunlight to study your opals, as this helps you see the colours properly. Keeping the opal wet can also enhance the visibility of the colours.

Imagine a piece of cheese with sauce between two buns. Spend time looking at the 'bun' from all angles to determine where the colour bar is brightest. Grind the host stone down to expose the brightest side of the colour bar while leaving a nice potch base underneath for support. If one side of the opal is naturally darker or has a black potch backing, remove the 'whiter' side to enhance the brightness.

Tips:

  • Wear old clothes and an apron, especially when cutting Boulder Opal.
  • Lay a towel over your legs to protect yourself from debris.
  • Grind around the sides of the opal to expose the colour bar without worrying about shaping it initially.

 

Step 3: Face the Opal

Once you’ve studied the opal and decided on the top side, mark it with a permanent marker. This process, known as "facing the opal," involves removing the top layer to expose the colour bar.

Using a trim saw can save time and preserve your grinding wheels. If the opal is small, or there’s minimal host stone, use a rough wheel to quickly grind away the potch. Stop just above the colour bar, pressing lightly to avoid chipping or scratching the opal. The flatter the colour bar, the easier it is to shape the opal. If the colour bar is wavy, use a Dremel tool to carve away the host stone and expose the colour.

Step 4: Shape the Opal

After facing the opal, start shaping it using a 360-grit sintered wheel, then move to a 600-grit sintered wheel. This will help expose as much of the colour bar as possible without removing too much opal, shaping the top into a nice cabochon.

You can either let the opal's natural shape guide you (freeform) or use a template and a tungsten scribe to draw the desired shape. Colouring the face with a permanent marker can help track the cutting process.

 

PROFILE - Surface "Cut" or Shape from Australian Opal Cutters on Vimeo.

 

Cut Light Opal Parcel from Australian Opal Cutters on Vimeo.

 

Step 5 [Optional]: Dop the Opal

Before doping the opal, flatten the back slightly to create a good surface for the wax. Use either a 360-grit or 600-grit wheel for this. Flattening the back now makes the final polishing easier and reduces the risk of accidental scratches.

Tips:

  • Wax won't stick to a cold stone.
  • Use a Dop Station or a Spirit Burner to warm the wax and the opal before attaching the opal to the dop stick.

Once attached, adjust the opal so that the back is evenly covered by wax and the opal is not touching the dop stick. Spin the dop stick to ensure the colour bar is perfectly horizontal, making the next shaping stages easier.

 

Step 6: Polish the Opal

Some people prefer to cut their opals in batches, pre-cutting and pre-shaping everything before polishing. This helps avoid contamination and unnecessary scratches.

Tips:

  • Press gently and use light pressure when polishing.
  • Regularly inspect your opal with a 10x magnification jeweler’s loupe.
  • Keep your cutting machine clean to prevent contamination, especially when frequently cutting Boulder Opal.

For final polishing, use a 600-grit, 1200-grit, and 3000-grit 'Nova' wheel. Keep the opal moving and spinning to avoid creating facets and deep scratches.

When you reach the final polishing stage, use a hard felt pad with a Cerium Oxide/water mixture. Keep the pad wet and the opal moving to achieve a high-quality polish. Use a jeweler’s loupe to check for scratches and ensure a smooth finish.

 

Polishing the opal from Australian Opal Cutters on Vimeo.

  

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