What is the causes for contaminated laps?
Ok, you are cutting and polishing happily away and then. Suddenly out of no where you are getting scratches across your facets. It is usually a really nasty series of scratches, at least for me. This is really a pain in the neck type of problem that every faceter will have happen to them sooner or later. Sorry, but it is just a matter of time if you facet enough.
There can be many causes, but the main cause of scratching is contamination on the lap(s). The contamination can be cause by quite a few things. But generally the list boils down to one of these three things. The stone you are polishing is brittle, and shedding chunks. This is not all that common but it does happen. Look at the leading or trailing edge of your stone and see if you can spot pits and comet trails. A chip at the leading edge of the facet with a larger to smaller scratch profile as the chip runs across the face of the facet is typical of this problem. This can be hard to tell for sure because often a contaminate on the