SedimentarySoil pH usually 5.0–6.0

Sandstone

A beach, a dune field or a river bar, buried and cemented — and visibly still made of sand.

How it forms

Rivers and waves sort sediment by size, and sand collects where the water is energetic enough to carry away the mud but not the sand. Bury it, and mineral-bearing water moving through the pore spaces precipitates cement around each grain.

Sedimentary — laid down in layers

Sediment settling through water in layers, then buried and compacted into rockwaterweight above squeezes the water out and cements the grains

Rock built from the wreckage of older rock, or from the remains of things that lived — sand, mud, shell and skeleton, settled in flat beds and buried until the weight turned them to stone. The only rocks that hold fossils.

What it is
Sand grains, mostly quartz, stuck together by a natural cement of silica, calcite or iron oxide. Rub a weathered face and grains come off on your hand.
How to know it
Gritty to the touch and visibly granular in good light. Bedding is usually obvious, and often curved rather than flat where a dune or a river bar migrated — that curved layering is called cross-bedding and it tells you which way the current ran.
How it wears
Crumbles back into sand along its bedding, and leaves overhangs and shelters where a soft layer sits beneath a hard one. Iron-cemented sandstone weathers to rust red.
What it means above ground
Sandy, quick-draining, usually acid soil. Sandstone is porous, so it stores groundwater and releases it steadily — sandstone country has reliable springs where the water table meets the hillside.
Where you stand on it
The Colorado Plateau and all of Utah's canyon country, the Appalachian Plateau, the Alberta foothills, and the Wisconsin Dells.
What lives on it
Pine, oak and heath on dry ground; the seepage lines at the base of the beds are often unexpectedly lush.
What it's used for
Building stone, paving, glass sand, and — in the Alberta foothills and Texas — the reservoir rock that holds oil and gas in its pore spaces.
What it does to the soil
Sours the soil above it — nothing in it neutralises rain, so the ground stays acid.

Next to it in the cycle

  • Quartzite

    sandstone cooked until the grains fused

  • Shale

    the mud that settled where the water was quieter

  • Granite

    where most of the quartz grains originally came from

Is this what you're standing on?

Find the rock under your town

Enter a town or postal code and we'll show you the rock beneath it and how old it is, the soil it makes, and the chain of rivers your water joins on the way to the sea.

General descriptions of rock families. Any particular outcrop can differ — rocks grade into one another, and a geological map at this scale describes a district rather than a hillside.