February’s Mineral: Goethite [FeO(OH)]

Posted by : Emily | On : February 1, 2014


Photo taken by Emily Halle

Actually pronounced GUR-tite and named after Johann Wolfgang von Goethe (the German poet, novelist, playwright, philosopher, politician, and geoscientist whose literary works include the influential Theory of Colours published in 1810), this iron rich mineral has been used since prehistoric times in pigmentation (such as yellow ochre) as well as iron ore in the production of steel.

Goethite is a hydrous ferric oxide, forming hematite when dehydrated and limonite upon further hydration. The colour is typically brownish black to black, yellow-brown, or reddish brown with an orthorhombic crystal structure. It is a common primary mineral in the upper oxidized zone of hydrothermal deposits and forms near surface as polymorphs of minerals such as marcasite, pyrite, siderite, and gypsum. The weathering of these iron-rich substances means that goethite is often a component of soil, as well as being precipitated by groundwater or other sedimentary processes – it can even be a byproduct of certain types of bacteria. Recently goethite has been identified on Mars by NASA’s Spirit rover, indicating that water must have existed on the planet at one time!

Metaphysically goethite is said to connect one with the Earth, strengthen the blood, enhance artistic creativity, and assist in the grieving process by uncovering wounds buried deep within the unconscious. Perhaps Johann Wolfgang von Goethe was referring to this when he penned the following passage in his poem The Holy Longing:

And so long as you haven't experienced
this: to die and so to grow,
you are only a troubled guest
on the dark earth.

The specimen pictured above is from Nova Scotia and is on display at the Museum of Natural History in Halifax.