When a gem has these threads, cutting it into facets might make it look kind of muddy.
当一块宝石拥有这些线状包裹体,切割成刻面型可能使它看上去有些模糊。
英语百科
Threading (manufacturing)
Threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods (many kinds of thread cutting and grinding, as detailed below); deformative or transformative methods (rolling and forming; molding and casting); additive methods (such as 3D printing); or combinations thereof.