Turgite

In modern usage turgite is often referred to as an iridescent "variety" of either hematite or goethite, but it was originally described (Hermann, 1844, 1845) as a new brown-red, dense mineral, with a blood-red streak, believed to be in-between hematite and goethite. A similar hydrated Fe(III) oxide phase was termed as 'hydrohematite' by Breithaupt (1847).

It was later described by Posnjak and Merwin (1919) as a fibrous mineral, variable in composition and "probably represents a solid solution of goethite with hematite with enclosed and adsorbed water". Such a solid solution seems unlikely however and it may need some study with modern methods. Based on X-ray diffraction studies (Böhm, 1928; Palache et al., 1944) it has been characterised as mixtures of microcrystalline hematite and either goethite or amorphous Fe hydroxide.

In more recent times, especially within the collector community, the name has also been widely used as a term for iridescent hematite or goethite (and sometimes as iridescent iron-staining coatings of indeterminate composition). Some iridescent hematite coatings are composed of aggregates of nano-sized rods of hematite (Lin et al., 2018); other reports suggest an aluminium phosphate (or less commonly aluminium arsenate) coating (Chi Ma and George R. Rossman, unpublished: http://minerals.gps.caltech.edu/manuscripts/in-prep/submitted/rainbow_hematite/ ). For photos of this material see: iridescent coating.

Originally described from Turjinskii Mine (Turginsk Mine), Turjinsk, Turya River, Krasnoturjinsk (Bogolovsk; Krasnotur'insk; Krasnoturyinsk), Ekateriinburgskaya (Sverdlovskaya) Oblast', Middle Urals, Urals Region, Russia. Under modern terminology the original material would be described as either hematite and/or goethite depending on analysis.

Any usage of this term should be discouraged.