This just in from the e-mail bag:
I started to facet this piece of Sunstone yesterday and when I used the 600 lap this strange surface appeared on this particular facet and it wouldn’t polish away, any idea what or why? What amazed me was that it only happened on this one facet, the stone is approx, 10 x 14 mm.
You usually see this sort of thing on Sunstone at the pre-polish level if you’re really close to a cleavage plane. Often, a sensitive faceter will detect this potential while cutting because these facets will feel softer than the rest – will cut faster, and over-cut quickly. The solution to getting a polish on them is:
- Reverse lap attack direction across the facet – either by reversing the lap itself, or by taking the stone to the “back” side of the lap.
- You may like to try a finer pre-polish before going to polish. Sometimes, that’s helpful.
- Use Voodoo polish – and in extreme cases, the 50k may be less prone to allow the scaling of the cleavage than the 14k.
Usually, a combination of these things will let you get a good polish – though we must sometimes settle for an over-cut facet in the process.