FacetLab is a free, open-source WebGL learning simulator from 4Cs.co.za. Inspect a rough diamond crystal, reveal inclusions, plan the proportions, polish the facets of a brilliant cut, and generate a finished 4Cs scorecard (cut, colour, clarity, carat). It runs entirely in your browser. Educational only: no signup, no pricing, no appraisal. Source open on GitHub.
