The volcanic granule

The volcanic granule are made from small holes lava. The size is 1-2cm , 2-4cm or 4-8cm etc. It's porous, hard and grey color, also can absorb sound ,dust and heat. It is used widely for water strainer, potted plant, sauna and barbecue etc. The volcanic granule is a ideal nature material.

This is some sample of volcanic granule and size is 2-4cm.

The volcanic granules are used for potted plant.