Coal Seam Trail is a hiking and biking trail in Boulder County, Colorado. It is 0.6 miles long and begins at 5,570 feet altitude. Traveling the entire trail is 1.2 miles with a total elevation gain of 195 feet. The Marshall Mesa Trailhead parking is near the trailhead. There are also restrooms. The High View Mine (elevation 5,584 feet) and Black Diamond Mine (elevation 5,627 feet) quarries can be seen along the trail.