Iridescent Turgite

What is Turgite

Turgite is a striking mixture of two iron oxide minerals, hematite (Fe₂O₃) and goethite (FeOOH), distinguished by its captivating iridescence. This iridescence, often manifesting in vivid hues of red, purple, green, and blue, arises from light interference caused by surface oxidation or thin-layer diffraction within the mineral's structure.

Turgite commonly forms in botryoidal (globular) or stalactitic shapes, often as a secondary product of the oxidation of iron-bearing minerals. Despite its aesthetic appeal, turgite is not recognized as a distinct mineral species by the International Mineralogical Association (IMA) because it lacks a unique chemical composition or crystal structure. Instead, it is considered a transitional or mixed form of hematite and goethite.

The name "turgite" originates from its initial description at the Turjinskii Mine (Turginsk Mine) in Russia. While scientifically classified as a mixture or variety of hematite and goethite, it remains highly sought after by collectors and mineral enthusiasts for its vibrant colors and unique forms.

Iridescent Turgite. Incredible Iridescent Hematite stalactite from Graves Mountain, Georgia. Photo: Anatoly Bitny

Turgite is a mixture of the two minerals due to the alteration of goethite, typically found in the botryoidal (globular) habit of the “parent” goethite; however, because it is a mixture of two minerals, it is not considered a mineral in itself.

Goethite is a common iron mineral. It often forms by weathering of other iron-rich minerals, thus is a common component of soils. It may form excellent pseudomorphs after the original minerals particularly pyrite or marcasite. Goethite may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits. When present in sufficient quantities, it constitutes an important iron ore mineral.

It apparently only occurs under specific environmental conditions because the pieces I collected in Nevada and brought home to New Mexico lost their luster and turned to dull gray hematite.

Turgite is a relatively rare mineral, but it can be found in many parts of the world, including the United States, Canada, Europe, and Australia. Some of the most notable occurrences of turgite include the Ironwood Iron Formation in Michigan, the Labrador Trough in Canada, and the Erzgebirge Mountains in Germany.

 

Turgite coated in a cave