It is the same as a metamorphic or marble limestone, in which grains or crystals forming it to various of marmarits making grains to, are visible with eye. In other words, Neyreez Porcelain stone refers to a stone that has whole-crystal texture and are mainly formed from calcite and a little amount of waltonite (as the main minerals). This term has been current in Iran for the last two decades and apparently has been told porcelain that it will give a porcelain sound in low thicknesses (about two centimeters) as it is hit by something.
The method of their extraction from the mine is in the form of wire cutting and mostly soft cutting and sometimes hard cutting. These stones have a low color variation, usually are white, or aura or yellow veins. They are strong and sanitary stones and they are found in almost every place in a building, even in places where there is a lot of water and especially in health centers. The word "crystal" is derived from the Chinese word among common people and refers to the metamorphic limestone (marble and porcelain) with its large crystals, and the color of the crystal stones are mostly dark gray.