Goethite Mineral: Facts, Properties, and Photos
What is Goethite?
Goethite is a naturally occurring iron oxide mineral that forms through the oxidation of iron in the presence of water and oxygen.
It takes on various forms and colours and can be found all over the world.
Goethite has been identified in abundance on Mars.
Goethite, named after the German poet, playwright and keen mineralogist Johann Wolfgang von Goethe, was first described in 1806.
It often forms through the weathering of other iron-rich minerals such as hematite and magnetite. Although usually black, it can occur in shades of yellow, brown or red, depending on the impurities present.
Fine crystallised goethite is rare but can be found in Cornwall, France, and Russia.
Goethite, which can be translucent to opaque, is commonly found in rust and iron ore deposits.
On the Mohs scale of hardness, goethite grades 5 to 5.5.
It can be found as needle-like crystals, but more commonly occurs in masses. In mineralogy, 'massive' crystal habit refers to a type of crystal growth where the mineral forms as a solid mass without visible external crystal faces.
Goethite has been used since ancient times and is a key component of the yellowish-brown pigment known as ochre.
Scientists study goethite to better understand Earth's weathering processes, particularly the breakdown of iron-rich minerals. It also helps to identify the conditions under which iron minerals form and evolve. Hematite, magnetite, and goethite are the most abundant iron oxides in nature.
Article Photos
The goethite mineral in the photo at the top of our article is on display in the Harvard Museum of Natural History, Cambridge, Massachusetts. The image is clickable and redirects to the original photo.
Pop-up photos: Hematite: Courtesy of Ron Wolf. Magnetite: Courtesy of Stan Celestian.
