... construction, engineering, mechanical processing etc. YWD 2290 consistent crystal color, regular shape, good trandparancy, high strength and ... , drilling, and grinding tools. YWD 2160 complete crystal shape with full surface, good diaphaneity and low impurity, high ... frame-saw and geological broaches. YWD 2140 comparatively regular crystal shape, high mechanic strength, beolonging to middle grade ...