File:Wyomingite lamproite (Lower Pleistocene, 0.95 Ma; quarry on volcanic cone on Zirkel Mesa, Leucite Hills Volcanic Province, NE of town of Superior, southwestern Wyoming, USA).jpg

English: Slightly vesicular wyomingite lamproite with abundant golden-brown phlogopite mica phenocrysts from the Pleistocene of Wyoming, USA (9.3 cm across at its widest).

The Leucite Hills Volcanic Province of southwestern Wyoming contains some of the rarest rocks on Earth. Each volcanic center in the Leucite Hills erupted lamproite lava. Lamproite is a rare, ultrapotassic & ultramafic igneous rock. It usually occurs in diatremes (= pipe-shaped igneous intrusions). Occasionally, gem-quality diamonds occur in lamproite diatremes. Various cinder cone volcanoes in the Leucite Hills erupted four types of lamproite lavas: wyomingite, orendite, olivine orendite, and madupite. Wyomingite is the most common Leucite Hills lamproite lithology - it is also the "official state rock" of Wyoming.

Wyomingite is an attractive rock, having numerous golden-brown phenocrysts of phlogopite mica. Other minerals in wyomingite rocks include leucite, diopside pyroxene, fluorapatite, and katophorite.

Locality: abandoned small quarry on the southern side of a cinder cone volcano on Zirkel Mesa, Leucite Hills Volcanic Province, northeast of the town of Superior, southwestern Wyoming, USA.

---

Example references on Leucite Hills geology:

Lange, R.A., I.S.E. Carmichael & C.M. Hall. 2000. 40Ar/39Ar chronology of the Leucite Hills, Wyoming: eruption rates, erosion rates, and an evolving temperature structure of the underlying mantle. Earth and Planetary Science Letters 174: 329-340.

Schultz, A.R. & W. Cross. 1912. Potash-bearing rocks of the Leucite Hills, Sweetwater County, Wyoming. United States Geological Survey Bulletin 512. 39 pp.