Sandstones contain many of the oil and gas deposits of the world...

Sandstone is often formed into strange shapes by the action of the wind.  The wind picks up individual sand grains and "blasts" them against rock outcrops.  The harder parts of the sandstone are left standing.

Sandstone forms very steep, near-vertical cliffs

Here is a sedimentary rock called "conglomerate".  The grains are too big to call this rock sandstone.  However, it is made of the same materials as most sandstones.  Conglomerate is very "poorly sorted".  This means it contains both larger and smaller grains.  Also note that the grain shapes range from rounded with high sphericity to angular with low sphericity.  See chart below.

Steep cliffs of sandstone

A well-sorted, coarse-grained sandstone

Laminations, or very small layers, in sandstone

More wind-blown sandstone shapes in Arches National Park, USA.

This is a coarse-grain sandstone which is made up mostly of the mineral quartz.  This sandstone is "well-sorted".  That means most of the grains are about the same size.  See sorting diagrams below.

Many sandstones are "friable".  This means that the grains are not well-cemented to each other.  They can be broken apart in your hands.

Here is a rock similar to sandstone, but the grains are much, much smaller.  The grains are clay-sized.  This rock is kaolinite, seen at high power under a scanning electron microscope

This sandstone is "poorly sorted".  This means it contains both larger and smaller grains

More wind-shaped sandstone monoliths.  The red color is always caused by small amounts of iron minerals in the rock.  The iron minerals "rust" when exposed to air, and stain the surface of the sandstone

A coarse-grained, poorly-sorted sandstone containing lots of mica and clay minerals is called "graywhacke" (gray-wacky)