SiO2>99.31%,low iron Hardness>8,more than French pebble Our own silica mine& ... grayish silica stoneSize: 2-4cm, 4-6cm, 6-8cm, 8-10cm, 10-12cm, 12-15cmApplication: Silica pebbles can be used as a grinding ... better sea freigth and prompt delivery.5. Negotiable package.6. Negotiable price on large purchase.Japanese customer's test ... made pebbles (round,1-2cm,2-4cm,4-6cm,6-8cm,8-10cm,10-12cm,12-15cm)