- The resistance of a substance to being scratched. Diamond is 10 in Mohs’ scale of hardness. Tests prove that diamond is approximately five to 150 times as hard as corundum, the next hardest mineral. The variation stems not only from the differences obtained from different hardness-testing methods, but also from the fact that various directions on a given stone’s surface show a considerable variation in resistance to abrasion. The hardest direction in diamond is parallel to the faces of the octahedron.
- Heart-shaped Brilliant
- A heart-shaped variation of the brilliant cut that is related to the “pear shape.” The round end is flattened and indented and the girdle widened until the length is approximately equal to the width.