FacetLab is a free browser-based diamond polishing simulator created by 4Cs.co.za Diamond Education. It helps learners explore the diamond 4Cs by turning a rough stone into a polished result through an interactive WebGL experience. Instead of only reading about cut, colour, clarity and carat, visitors can experiment visually and see how choices affect the final stone. The project is open source and designed for students, jewellery-curious beginners, teachers, and anyone who wants a simple practical introduction to diamond grading concepts. The tool runs directly in a modern web browser and does not require installation, downloads, or special equipment.