Soils and layers
Lava rock (scoria)
Reusable
Light, porous red volcanic rock. Moss grips it well.
What the simulation uses
- Holds water
- 17.5 % by volume
- Water it keeps after draining; the rest runs down to the drainage.
- Pore space
- 55 % by volume
- Room for air and water between grains; low means roots suffocate when wet.
- Weight
- 900 g/L
- How heavy a litre is.
- pH
- 6.8 to 8 pH
- How acid it keeps the soil.
- Mould risk
- none
- How much fresh food it gives white mould; high-risk soils fuzz over in the first weeks.
- Nutrients
- low
- Plant food it brings.
- Presses down to
- 97 % of its loose depth
- How far pressing can pack it, keeping its weight.
Description
Bubbly volcanic rock, heavier than pumice, so most pieces sink. Chunks run from about one to three centimetres, good for drainage or small rockwork. It adds a few trace minerals and barely touches pH.
Also called red lava rock, black lava stone, volcanic rock.
Estimated, where sources were thin: bulk density, water holding and pH not measured on a cited page; basalt solid 2.4-3.1 g/cm3 (Engineering ToolBox) bounds it.