luster is an important quality standard for decoration stone.  The luster depend on the refractive index of all kind of mineral which consist of the rock, also depend on the micro structure of the stone surface.

      The same granite rock, its mineral content is almost the same.  The surface is more smooth, then the luster is more, the stone surface’ micro structure is depend on the polish quality, so when purchase the granite stone, how to distinguish the polish quality is very important. If not grasp some skill, its very difficult to tell which is good. As from our eyes, all the surface are bright like mirror, but actually, even the stone surface is so smooth, if viewing through high grade microscope, you will see the micro-structure are rough and not smooth, even some exist great defect.

      Viewing through high grade microscope, could see concave pit, strip, and track after polish processing.  These are caused because of mineral defect itself, it is not be able to avoid. And some are caused because the grinding stone the grain grade is not reasonable or not polished so well.

      To observe the tiny defect, we must be very careful, and need to grasp some skill and method. We could put the stone surface under the sunlight lamp or sun, observe its reflecting surface, then could see clearly these kind of concave and strip, if it is because of the mineral, we could ignore it, but if it is because of the bad polish, then had better to avoid to purchase this kind of stone.

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