flint pebbles 1)2-4,4-6,6-8,8-10,10- ... hardness 5)bearable 6)competitive pri 1.Product:Pebbles/Man made pebbles/Flint pebbles/Silica pebbles/Cobblestone/Natural pebblesSiO2 99.31%Al2O3 0.33 ... . We manufacture all sizes and grades of flint pebble(pebbles),natural pebbles(cobblestone),silex blocks(bricks),which are regarded as the most ...