Pike County Gulch is a coastal valley in Marin County, California

Marin County, California

Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, which is associated with a small stream. It is located between Wilkins Gulch

Wilkins Gulch

Wilkins Gulch is a valley in western Marin County, California, United States, located northwest of Pike County Gulch. It is associated with a small stream....

 (to the northwest) and Audubon Canyon

Audubon Canyon

Audubon Canyon is a coastal valley in Marin County, California, United States, which is associated with a small stream. The canyon provides habitat for a variety of animals and plants...

 (to the southeast).

The stream descends the western slope of the Bolinas Ridge

Bolinas Ridge

Bolinas Ridge is a north-south ridge in southwestern Marin County, California. Much of the western side of the ridge is protected parkland in the Golden Gate National Recreation Area, and the eastern side is watershed lands of the Marin Municipal Water District....

, crosses State Route 1

California State Route 1

State Route 1 , more often called Highway 1, is a state highway that runs along much of the Pacific coast of the U.S. state of California. It is famous for running along some of the most beautiful coastlines in the world, leading to its designation as an All-American Road.Highway 1 does not run...

 about 3 miles (5 km) north of Stinson Beach, California

Stinson Beach, California

Stinson Beach is a census-designated place in Marin County, California, on the west coast of the United States. Stinson Beach is located east-southeast of Bolinas, at an elevation of 26 feet . The population of the Stinson Beach CDP was 632 at the 2010 census.Stinson Beach is about a 35-minute...

, and drains into the northern tip of Bolinas Lagoon

Bolinas Lagoon

Bolinas Lagoon is a tidal estuary, approximately in area, located at in the West Marin region of Marin County, California, United States. It is a part of the Gulf of the Farallones National Marine Sanctuary. The lagoon is a back bay of Bolinas Bay on the Pacific coast approximately 15 mi ...

.

The gulch contains an ore vein 4 feet (1.22 m) thick containing pyrite

Pyrite

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...

, located a mile (1.6 km) south of the Union Gulch Mine.