Ethiopian Welo opals are the ideal stone for learning how to cut opals: the rough stone is affordable, the material is astonishingly forgiving for an opal – and hardly anything is more satisfying than bringing out the play of color layer by layer from an unassuming rough stone. After about 15 years at the cutting machine, I'm sharing the most important basics here.

Why Welo Opal is Perfect for Learning

• Forgiving of mistakes: Welo opals generally have significantly thicker color bars than Australian opals. A beginner's mistake rarely costs the entire stone.
• Inexpensive rough stone: Practice material is available for just a few francs per gram – unthinkable with Australian black opal.
• The play of color guides you: Because Welo opals are often translucent, you can see early on where the color is and in which direction you need to work.

The Special Feature: Hydrophane and Water

Welo opals are hydrophane opals – they absorb water. However, when cutting, you must work wet (more on this below). This means: your stone will look different while working than in its final state. It will become more transparent, and the play of color may temporarily disappear. Don't panic – this is normal. Let the stone dry at room temperature for a few days after cutting, then the true result will show. Therefore, never judge your progress on the wet stone.

A tip from me to prevent cracking: Cut the stone in one pass, or rather, don't let it dry in between. When you are finished, wrap it in absorbent kitchen paper and seal it airtight in a Ziploc bag for one to two days before removing it and allowing it to dry completely. This way, the stone dries very slowly at first, and you minimize the risk of cracking.

The Equipment

• Grinding machine (cabbing machine with wheels in my case) with water supply – a flat lapping machine also works
• Diamond wheels in several grits: hard 280 for shaping, soft (280) for fine shaping, soft medium (600–1200) for refining/pre-polishing, optional: soft fine (3000–14000). Usually, you can polish directly after 1200 grit.
• Polishing wheel made of leather or felt with cerium oxide, preferably Super, or French Cerium oxide with 1 nM or less.
• Dop sticks and dop wax to hold the stone securely.
• Waterproof pen, good lamp, patience.

Step-by-Step to the Cabochon

1. Read the rough stone: Examine the stone wet and dry, from all sides, under a lamp. Where is the play of color? Are there cracks or sand inclusions? Plan the cut so that the best color layer will be on the top of the cabochon later.
2. Rough shaping (280 hard): Saw or grind the rough stone to the approximate shape. Always work with running water and light pressure – the stone should never get hot.
3. Dopping: Glue the stone onto the dop stick with dop wax. For Welo opals, use the wax only lukewarm – they don't like too much heat.
4. Dome grinding (280 hard and 280 soft): Work out the cabochon dome. Use even, flowing movements; regularly check the symmetry from above and from the side.
5. Refining (600–1200): Remove all scratches from the previous grit before moving to the next. This is the most important rule of all – a 600-grit scratch cannot be removed with the polishing wheel.
6. Polishing: The final shine is achieved with cerium oxide on leather. For opals, it's better to work longer with light pressure than briefly with heavy pressure.
7. Let dry and enjoy: Only after a few days will the stone show its final play of color.

Safety: Always Grind Wet

Opal consists of silica. Dry grinding dust should not be inhaled – when ground wet, virtually no dust is produced. Therefore, always work with a water supply and ensure good ventilation. I also always wear a respirator.

The Most Common Beginner Mistakes

• Too much pressure – the stone gets hot and can develop tension cracks.
• Skipped a grit – scratches that remain visible during polishing.
• Judged the wet stone – and disappointedly continued grinding too deeply, even though the color would have been perfect after drying.
• Ground away the most beautiful color layer because the rough stone was not carefully "read" beforehand.

Looking for the Right Rough Stone?

You can always find suitable rough stones for practice in my rough stone collection – and if you want to see what the result looks like first: Here are my finished opals.