The Mazaruni River is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in northern Guyana

Guyana

Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...

, running from its source in the remote western forests of the Pakaraima Mountains to its confluence with the Cuyuni River

Cuyuni River

The Cuyuni River is a South American river and a tributary of the Essequibo River. It rises in the Guiana Highlands of Venezuela where it descends northward to El Dorado, and turns eastward to meander through the tropical rain forests of Guayana Esequiba...

 near Bartica

Bartica

Bartica, Essequibo is a town on the left bank of the Essequibo River in Cuyuni-Mazaruni , at the confluence of the Cuyuni and Mazaruni Rivers with the Essequibo River...

. As it descends from the Guiana Highlands the river runs south-east, past Issano, then northward to Bartica.
The river is a source of alluvial gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

.
The Mazaruni River takes source in the Roraima Plateau, three levels of sandstones and conglomerates, crowned by Mt. Roraima

Monte Roraima

Mount Roraima is the highest of the Pakaraima chain of tepui plateau in South America. First described by the English explorer Sir Walter Raleigh in 1596, its summit area is defended by 400-metre-tall cliffs on all sides...

 (2810 m.).