How to evaluate the grinding and polishing quality of granite stone

2022-08-30

The gloss of the veneer stone is an important criterion for evaluating the quality of the stone. The size of the gloss depends on the refractive index of the various minerals that make up the rock on the one hand, and is closely related to the microstructure of the stone surface on the other hand. The mineral composition of the same granite stone is certain, the smoother the surface, the fewer the convex defects, and the higher the gloss of the stone. The microstructure of the stone surface is determined by the quality of the grinding and polishing process. Therefore, when purchasing granite stone, it is very important to distinguish the quality of stone grinding and polishing. If you don't master some skills, it is a very difficult job to identify the quality of grinding and polishing, because the surface of all veneer stones is as bright as a mirror to our naked eyes. However, no matter how smooth the surface of the veneer stone after grinding and polishing actually looks, its microstructure is rough and uneven after being magnified by a high-power microscope, and sometimes there are large defects.

The surface of the granite stone that is as smooth as a mirror to the naked eye can be seen under a reflective microscope and a scanning electron microscope. There are pits and streaks left after grinding and polishing on the stone surface. Some of the marks are caused by the defects of the mineral itself that cannot be overcome under the current processing conditions, and some are caused by the unreasonable thickness of the grindstone or the incomplete grinding and polishing during the processing.

To observe these very subtle defects, we need to be very careful and meticulous, but also to master certain methods. We put the surface of the processed stone against the sunlight or fluorescent lamp, and observe the reflective surface to clearly find various pits and streaks as shown in the figure. For those irregular small pits, some of the minerals may be composed of stone. If you find some regular streaks on the surface of the stone, it is caused by the poor processing quality. You should try to avoid such stones when purchasing.

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