Stones and wood

White river stones

Smooth white stones, tumbled round.

What the simulation uses

Holds water: 1 % by volume; Water it keeps after draining; the rest runs down to the drainage.
Pore space: 3 % by volume; Room for air and water between grains; low means roots suffocate when wet.
Weight: 2550 g/L; How heavy a litre is.
pH: 7 to 7.5 pH; How acid it keeps the soil.

Smooth white stones, tumbled round. They hold no water and stay neutral, so they work anywhere you want a bright accent.

Also called white pebbles.

Estimated, where sources were thin: look authored for the app; physical values estimated.