Siltstone has very few uses. It is rarely the target of mining for use as a construction material or manufacturing feedstock. The intergranular pore spaces in siltstone are too small for it to serve as a good aquifer. It is rarely porous enough or extensive enough to serve as an oil or gas reservoir. Its main use is as a low-quality fill when better materials are not locally available.

Extraterrestrial Siltstone?

As NASA and the space agencies of other countries explore the moons and planets of our solar system, they are finding many examples of sedimentary rocks. Some of these are thought to be deposited by water, but some are also thought to have been deposited by winds.

As an example, in the Gale Crater of Mars, NASA’s Curiosity Rover photographed an outcrop of sedimentary rocks that is believed to be made up of interbedded shales and siltstones – based upon the size of the grains in the rocks (see accompanying photo). In outcrop, these rocks look almost exactly like outcrops of shales and siltstones here on Earth. However, their grains and cementing agents are likely different from most of the sedimentary rocks found here on Earth.