English: 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.