... in the water treatment hard duarble,high quality Garnet Sand filter material ItemDataItemDataSpecific gravity3.9g/cm3Acid endurance96%Volume weight2.5g/ ... 2mm,2-4mm,3-6mm,4-8mm,5-10mm Gravel and water filter pebble is composed of sub-angular,hard durable , ... finest availble in the world for water filtration applications.Our filter gravel is washed,clean dried,and screened to meet exacting specification ...