... Hardness>8,more than French pebble Our own silica mine&factory Professional manufacturer for 30 years 1. Product ... grayish silica stoneSize: 2-4cm, 4-6cm, 6-8cm, 8-10cm, 10-12cm, 12-15cmApplication: Silica pebbles can ... 8Porosity<=0.38%Actual abrasion rate of pebble<=1.35Appearance of pebbleRound(ellipse)Color of product ... silica man-made pebbles (round,1-2cm,2-4cm,4-6cm,6-8cm,8-10cm,10-12cm,12-15cm)