... , also suitable for geological drills.YWD 2180 complete crystal shape, perfect cubic octahedron, good diaphaneity, high impact ... cutting, drilling, and grinding tools. YWD 2160 complete crystal shape with full surface, good diaphaneity and low impurity, high ... -saw and geological broaches. YWD 2140 comparatively regular crystal shape, high mechanic strength, beolonging to middle grade, containing ...