Stewartville and Ridge Trail Loop

Black Diamond Mines Regional Preserve

Level: Moderate
Total Distance: 7.0 miles round-trip
Hiking Time: 3.5 hours
Elevation Change: 1,500 feet

Black Diamond Mines Regional Preserve is a strange mix of elements—human history combined with natural history, wild green hills juxtaposed with industrial complexes north of the park, rare species of plants commingled with nonnative flora planted by settlers in the late 1800s. The 3,700-acre park has many moods and puts on different faces in changing seasons and weather conditions. This seven-mile loop reveals some of its highlights and adds some good exercise to the bargain.

Begin your trip at the trailhead at the end of Somersville Road. Take the paved road from the gate at the parking lot, walk about 50 yards, then turn left on signed Stewartville Trail. Named for one of the coal-mining towns that thrived in this area in the late 1800s, Stewartville Trail is a wide dirt road that climbs moderately and steadily uphill. As you hike through open grasslands, you'll pass some nonnative trees that the miners planted—pepper, eucalyptus, almond, and locust. The almond trees produce fragrant flowers in the spring.

A 0.5-mile climb brings you to a cattle gate at a high point on Stewartville Trail. Go through the gate and admire the deep, green, grassy valley below you. The good news is that you're going to hike into that bucolic valley; the bad news is that you'll have to climb back out of it. On the far side of the gate, turn right to stay on Stewartville Trail. (The return of your loop is Ridge Trail, on your left.) Mount Diablo looms large to the south.

As you start to descend, watch for the single-track cutoff for Miners Trail; bear left on this trail and leave the wide roads behind. Miners Trail is a narrow, well-built footpath that descends along the shoulder of the canyon wall, cutting across its steep slope. It leads through a surprising grove of gnarled foothill pines and coulter pines. Black Diamond Mines Preserve is noted as the northernmost location of coulter pines, black sage, desert olive, and dudleya.

Where Miners Trail touches down to the valley floor, continue straight ahead to rejoin Stewartville Trail. Down in this valley, you'll hear nothing but wind and the sound of your own breathing. It's hard to imagine that this wide-open space was once the site of a bustling community.

Bear left on wide Stewartville Trail. In 0.5 mile you'll pass Stewartville Trail Camp, a hike-in camp that can be reserved by individuals or groups who are willing to hike, bike, or ride horses into the camp. At a junction with single-track Star Mine Trail, consider adding on a 1.5-mile loop trip to see the closed-off tunnel of Star Mine, one of the last active coal mines in the area. (The loop will bring you back to Stewartville Trail.) Or continue straight ahead for 0.25 mile, passing an outcropping of colorful boulders that is lined with swallow's nests, to the left turnoff for Prospect Tunnel.

The tunnel's spur trail leads a few hundred yards to an obvious opening in the hillside. You can explore about 150 feet into the mine shaft before you reach a steel gate. The air inside its sandstone walls is a little musty, but always cool. Tall hikers will have to duck their heads. Daylight penetrates the entrance, but a flashlight is necessary if you want to travel more than a few feet. The tunnel was driven in the 1860s by miners in search of coal ("black diamonds").

Back on the main path, follow Stewartville Trail for nearly a mile farther, climbing gently, then make a sharp left turn on Ridge Trail. You're leaving the valley now and beginning the steep ascent back to the trailhead. The roller-coaster Ridge Trail dips down occasionally but more often rises steeply. The climb is eased by the sudden appearance of views to the north of Carquinez Strait, Suisun Bay, Pittsburg, and Antioch.

When at last Ridge Trail returns you to the gate at Stewartville Trail, consider a rest on the bench by the gate. Once again, pause to admire the green valley below. Then it's an easy 0.5-mile stroll back down Stewartville Trail to the trailhead.

Sometimes you just don't want to see another soul, and that's not always easy to do in the San Francisco Bay Area. But there's a hiking trail in Black Diamond Mines that is rarely visited because it's not in the main trail region of the park. The loop is a figure eight around Lougher Ridge, and it begins behind a park residence across the road from the main park office. If you hike just the outside of the figure eight, it's a three-mile loop, but one of the best areas is the cross-section, which provides high views from a 1,100-foot ridge. What's so great about Lougher Ridge Loop? Grasslands, spring wildflowers, views to Carquinez Strait, and most importantly, solitude.

From Highway 4 in Antioch, take the Somersville Road exit south. Drive 3.8 miles south on Somersville Road to the end of the road and the trailhead. (You'll pass the park entrance kiosk at three miles, then continue another 0.75 mile to the trailhead.)

Information and Contact
A $5 day-use fee is charged per vehicle on weekends and holidays. Leashed dogs are allowed ($2 dog fee). Bikes are allowed on fire roads only. A free map is available at the entrance kiosk or by download at For more information, contact East Bay Regional Park District, 2950 Peralta Oaks Court, P.O. Box 5381, Oakland, CA 94605, 510/544-2750 or 888/327-2757,

From the book Moon 101 Great Hikes of the San Francisco Bay Area by Ann Marie Brown. Excerpted by arrangement with Avalon Travel, a member of the Perseus Books Group. Copyright © 2011. For more information, visit


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