Black Diamond Mines Regional Preserve is in Contra Costa County south of Antioch and Pittsburg and west of Brentwood, at the eastern edge of the Diablo Range. The area was a center for coal (black diamond) mining in the second half of the 19th century, with 5 towns in the immediate area. The preserve is about 6000 acres, with 60 miles of trails. On this visit, my first, I hiked a 6.2-mile loop with 1650 feet of elevation gain and loss, starting at the Somersville townsite at the end of Somersville Rd.
The parking area and trailhead are at the upper end of Markley Canyon, where Somersville Rd has climbed from sea level to 700 feet in about 4 miles. The loop route I chose goes counterclockwise, following the Nortonville, Black Diamond, Manhattan Canyon, Chaparral Loop, Pittsburg Mine, and Stewartville Trails. The trails in the preserve are well-signed at junctions, so it is straightforward to follow a pre-selected route.
From the trailhead Nortonville Trail climbs 400 feet in nearly 1 mile to Nortonville Pass.
Along the way there is a short side loop to Rose Hill Cemetery, on the southeast-facing slope of Rose Hill. This was a Protestant cemetery that served all 5 local coal-mining towns. Although it is believed that there are at least 235 burials in the cemetery, today there are only about 80 gravestones. This view is looking east toward a hill on the other side of Markley Canyon.
After summiting Nortonville Pass, the trail descends to a Tee intersection at the Nortonville townsite. From there I turned left and followed Black Diamond Trail for about 3 miles. About ¼ mile from Nortonville is the location of the Black Diamond Shaft hoisting works. The Black Diamond mine was the largest in the Mt Diablo coal field.
There are several other mining location artifacts in the park, and I was fortunate to visit a few of them. About ¾ mile past the Black Diamond Shaft, just off Coal Canyon Trail, is Jim’s Place, a small one-room dwelling hollowed out, like a cave, in the hillside.
The trail, here a paved road, climbs for another half mile or so to the edge of the preserve, beyond which there is a cluster of communication towers on a hilltop. The presence of these towers, as well as electric transmission towers and lines within the preserve, provides a stark contrast to the mining remnants.
On the way up the road there were great views of Mt Diablo, only about 5 miles away to the south.
The highest point on the trail is about 1600 feet elevation. From this location there was a spectacular view of the large wind power farm across the lower Sacramento River in Solano County.
The Black Diamond Trail leaves the road and descends. Briefly I could see a bridge I didn’t recognize, which turned out to be the Antioch Bridge that carries CA-160 across the Sacramento River. About 0.3 mile from the top there are a few small roller-coaster hills, with particularly nice views of the Domengine Formation, the 52 million year old sandstone that contains the coal deposits.
For a January hike, the golden brown hills were yet another reminder of the almost totally dry year in the area. Also, the temperature was relatively warm for January. Still, I was startled to notice that some trees were starting to sprout spring foliage On the calendar, there were still 2 months of winter remaining.
About 1 mile past the highest point of the Black Diamond Trail there was a nice view of the rolling hills of the preserve.
Another 0.4 miles further there is a junction with the Manhattan Canyon Trail, which I followed down the canyon to the right. This part of the trail was steeper. There were a couple of sections built as steps, and there was more shade in the canyon. I was keeping an eye out for different types of manzanita, and I found this type with greyer, stemless leaves that may be Mt Diablo manzanita, found only locally on and near Mt Diablo.
About 0.3 mile down the Manhattan Canyon Trail there is a footbridge across a (dry) stream, where I turned sharp right on the Chaparral Loop Trail and started to climb again. At the top of this climb there was another transmission tower, where I turned left to stay on the Chaparral Loop, and descend once again. In this area the trail was on smooth, almost-bare rock. A slight layer of fine rock dust made footing challenging, given the nearly 15% grade. I noticed some chirping and rustling in the chaparral, and eventually got a good view of a small bird that perched momentarily on top of another Mt Diablo manzanita. I’m pretty sure this is a Hutton’s vireo.
One of the reasons I hiked the Chaparral Loop Trail was to pass by additional mining artifacts. In this area of the preserve there was sand mining, starting in the 1920’s after the coal mining stopped. A small cave-like excavation was called the Powder Magazine, where explosives were stored. About 0.1 mile away is the Hazel-Atlas Portal, the entrance to a sand mine. If you walk on the tracks up to the entrance you can see into the tunnel. I believe this is accessible on guided tours, as there is a light and even a trash receptacle inside the gate.
From here I followed the Pittsburg Mine Trail for about 0.3 mile to Stewartville Trail, where I turned left to return to the trailhead. Along the Stewartville Trail I had a pretty view across the Markley Canyon toward Rose Hill and the cemetery, with the Nortonville Trail and the cemetery access trail visible on the hillside. There is an interesting illusion in this picture, due to the sloping hillside: it seems that the vantage point is higher than the cemetery, but in fact it is about 250 feet lower.
When I arrived back at the trailhead I observed western bluebirds and Oregon juncos around the picnic tables. There is also a display for the Independent Mine, the northernmost mine in the Mt Diablo coal mine field.
I thoroughly enjoyed learning some local mining history while hiking in this East Bay Regional Park District preserve. It will be interesting to return another time, perhaps after some rain and the hills are a more normal winter-time green. I can imagine that would be spectacular.