Remember in school when you were learning about Pi, and thinking “I’m never going to need this in my life”? The lapidary is one of the professions where these calculations are used on a daily basis.
Last week we talked about re-polishing stones, this week we’re focusing on cutting.
Cutting a stone from rough material requires patience and attention to detail. The lapidary first has to figure out which part of the crystal to cut, which is easier for some stones than others.
They need to consider:
- Where are the fewest inclusions?
- How can I get the best yield?
- How the colour distribution will end up if there is colour zoning
- Is there cleavage (natural breaking directions of a crystal)? Will the stone fall apart?
Once these questions are answered, they need to work out mathematically where they saw through the material, and at which angles the facets need to be. Cutting cabochons is easier but still requires thought. For some more difficult jobs, the lapidaries will create a diagram before beginning the work, and when cutting they will tick off the number of facets they have done. Round brilliant cuts must have 57 facets, or 58 with a culet, so they need to make sure they are precise.
Algebra and trigonometry are a lapidary’s best friend. They have to be so precise – the tiniest fraction of a millimeter wrong and the whole job is a bust.
A typical, very simplified, process for cutting is this:
- Saw off the piece from the rough (unless you’re cutting the whole piece of rough)
- Create the pre-form – the general rough outline of what the overall shape will be
- Using a lap, they will grind and polish the material into the right shape with the correct facets (it’s really cool when you can begin to see a stone take its shape!)
- The stone is ready for its final polish!
Our clients ask us to cut rough material for 2 main reasons: it’s sentimental, or it’s profitable. Something to bear in mind however is that cutting is an expensive skill, so it is not always profitable. We are always happy to discuss this with you in our showroom.