... , and ultra-high shell content.Physical and chemical performance indexSpecific Gravity: 1.28 Hardness: 2.5-3 .0 MOH Acidity: 3 ... regeneration, economic and durable and so on.Uses: It is used for oil field, refining, environmental protection, chemical industry wastewater treatment ... spectecles, jewelry, button, stamping parts, electronic parts, etc. Walnut shell used as polishing material