1. Observe the surface structure. Quality stones are consistent in texture and dense or compact in structure, Check the edges are defective or not.
2. Draw or measure the size in case it will effect the joining.
3. Knock the stone and listen to the sound. Generally speaking, those in high quality and dense structure will make a light sound.
4. Samples may differ from the actural stone, especially when you are selecting those that vary widely in appearance.