Sandstone
Cemented sand — the most-used building stone in much of the world, and the rock that holds most groundwater and oil.
Sandstone is sand grains cemented together, and almost all of those grains are quartz — because quartz is what survives. Feldspar weathers to clay and micas break down, but quartz is hard and chemically stubborn, so it accumulates while everything around it disappears.
What distinguishes one sandstone from another is mostly the cement between the grains rather than the grains themselves. Silica cement gives a hard, durable stone; calcite cement gives one that dissolves in acid rain; iron oxide cement gives the reds and yellows of desert sandstones and a moderate durability between the two.
How it forms
Sand accumulates wherever water or wind sorts sediment by size — beaches, river channels, deltas, dunes — and is then buried, compacted and cemented by minerals precipitating from groundwater passing through the pore space.
That pore space is what makes sandstone economically important beyond building. The gaps between grains hold water, oil and gas, and connected pores let fluids move through, so most of the world's aquifers and a great many petroleum reservoirs are sandstone. A rock defined by what is not in it.
Uses
As dimension stone it is among the most widely used building stones, easy to quarry in beds and soft enough to cut and carve with hand tools while still weathering well when laid on its natural bed.
Crushed, it is an aggregate and a source of silica sand for glassmaking and foundry moulds. Its subsurface role is larger still: sandstone aquifers supply drinking water across large regions, and sandstone reservoirs hold much of the world's produced oil and gas.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
is composed of
- Quartz — mineral · almost all sandstone grains are quartz, because quartz is what survives weathering
- Calcite — mineral · as cement between the grains in calcareous sandstones
- Orthoclase — mineral · as detrital grains in arkosic sandstone, where feldspar survived transport
is a source for
- Dimension stone — material · among the most widely used building stones
- Sand — material · read backwards: sandstone is cemented sand, and crushing it back to grains is one route to manufactured sand
is used in
- Construction — industry · as building stone and as a source of construction sand
is an input to
- Quarrying — process · worked along its bedding, which parts more cleanly than any cut across it
is sourced from
- Granite — rock · the quartz grains are what survives the weathering of granite and gneiss; everything softer in the parent rock became clay and went elsewhere
Sources
- Material WorldOur own writing