Hematitic sand and sandstones are mainly consisting of quartz but these quartz grains have an intense pink, orange or red color. The coloring agent in this sand is volumetrically insignificant – it is hematite (oxide of iron) that forms very thin rust-colored pigment on larger silicate grains.
However, its influence on the appearance of sand or sandstone is very strong. A well-known example of such sand is the Coral Pink Sand Dunes in the State of Utah, USA. Devonian sandstones (Old Red) in many places are often even darker (brick red). These sandstone formations are known throughout the world as “red beds”.
Hematite is not a detrital mineral (formed as a result of disintegration of a parent rock) in this sand type. It is mainly groundwater that carries iron and forms ferric gel on silicate grains. Complete dewatering of such gel results in a thin layer of iron oxide. Hematitic sand is very common in deserts.
Desert sand is often reddish in color due to fine-grained hematite covering quartz grains. Erg Murzuk, Libya. Width of view 15 mm.
Sand dunes in Sahara (Morocco) are not gray or white as one would expect pure quartz sand to be. Instead they are orange. This color is a combination of white quartz and reddish hematite.
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