Sandstone

What is sandstone?

Sandstone is a clastic sedimentary rock composed mainly of sand-sized grains. Quartz and feldspar are common, while the cement may be silica, calcite, iron oxides or clay minerals. The exact composition gives each sandstone its own hardness, porosity and colour.

Structure and appearance

Sandstone may be cream, yellow, red, brown, grey or green. Iron oxides often create red and orange tones, while bedding, cross-bedding and changes in grain size produce lines and natural movement. Some varieties are fine and even; others show coarse grains and a more pronounced surface texture.

Formation and localities

Sandstone forms when sand accumulates in rivers, deserts, beaches, deltas or shallow marine environments and is later compacted and cemented. It occurs on every continent and is commonly associated with layered sedimentary basins.

Use in mosaic

In stone mosaic, sandstone contributes earthy colours and visible grain. It is useful for architectural backgrounds, landscapes and broad areas where a softly textured surface is desirable. The maker must account for differences in porosity and polish between varieties.