Bronze colored crystal aggregates of bartonite from California (Coyote Peak, Coastal Range, Humboldt County, California, United States of America). Bartonite is a very rare potassium sulphide with formula K6Fe20S26S, only known from 6 localities worldwide, this one being from the type locality in Coyote Peak. Potassium is a very rare element in sulphides: of more than 5000 mineral species known only 5 are potassium sulphides. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Bartonite
Bartonite is an IMA-recognized mineral species in the sulfide class, with the chemical formula K₆Fe₂₀S₂₆S.
It crystallizes in the tetragonal crystal system (space group I4/mmm). It is a member of the Djerfisherite structural group.
Key properties: Mohs hardness 3.5; specific gravity 3.305; Black streak; Submetallic luster.
IMA symbol Btn, IMA status: approved, named in 1977.
Found in clots with other sulfides and silicates in an alkalic diatreme which intruded Franciscan rocks.
It is found associated with Rasvumite, djerfisherite, erdite, pyrrhotite, pyrite, sphalerite, löllingite, magnetite, nepheline, phlogopite.
The name refers to Paul Booth Barton, Jr. (1930–), ore petrologist with the U.S. Geological Survey.