1, size: 2-4,4-6,6-8,8-10,10-12,12-15cm 2, high silica content 3, good hardness 4, bearable 5, best price, fast delivery 1.Product:Pebbles/Man made pebbles/Flint pebbles/Silica pebbles/Cobblestone/Natural pebblesSiO2 99.31%Al2O3 0.33%Fe2O3 0.028%MgO 0.04%CaO 0.09%INSPECTATION PRODUCTFLINT PEBBLESIZE OF PRODUCT8-10CMSTANDARD ABRASION RATE OF SILICA PEBBLE< 1.5ACTUAL ABRASION RATE OF SILICA PEBBLE1 ...