---
title: Basalt in a terrarium | Glass Jar Garden
description: Basalt: Dark, fine-grained volcanic rock in blocky chunks. In the jar it has holds water 1 % by volume, pore space 3 % by volume, weight 2550 g/L.
url: https://glassjar.garden/guide/hardscape/basalt/
---

Stones and wood

# Basalt

Dark, fine-grained volcanic rock in blocky chunks.

## 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.)

## Description
Dark, fine-grained volcanic rock in blocky chunks. It is dense, holds almost no water and has no real effect on pH.

Also called columnar basalt.

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

[Grow it in a jar](https://glassjar.garden/?guide=hardscape/basalt)

[Black lava rock](https://glassjar.garden/guide/hardscape/black-lava-rock/) · [All stones and wood](https://glassjar.garden/guide/hardscape/)