English: Gilsonite (uintaite) dike in the Tertiary of northeastern Utah, USA.

Gilsonite (a.k.a. uintaite) is a variety of asphaltite - it's a solid hydrocarbon - basically solidified oil. Gilsonite usually has the appearance of obsidian or anthracite coal. It is jet black in color, very lightweight, brittle, and has a conchoidal fracture. The largest “deposits” of gilsonite in the world are in the Uinta Basin of northeastern Utah, USA. Gilsonite occurs there as vertical NW-SE trending veins intruded within the Eocene-aged Uinta Formation. The source of the hydrocarbons is organic-rich beds in the underlying Green River Formation (Eocene) and Wasatch Formation (Paleocene).

Gilsonite is not readily combustible and is not a fuel, but it does have economic value. Gilsonite is mined in northeastern Utah and processed and is used in numerous products and applications (e.g., see: www.geospectra.net/kite/gilsonite/gilson.htm).

This photo shows an active gilsonite mining operation (as of June 2013) developed on the Cowboy Dike intruding the Uinta Formation. The dike was probably emplaced ~10 to 30 million years ago.

Locality: gilsonite mining operation ~2.8 air miles almost due north of the town of Bonanza, eastern Uintah County, northeastern Utah, USA (40° 03’ 28.34” North latitude, 109° 10’ 11.44” West longitude)