031 is a hiking, biking, and horse trail in Lyon County, Nevada. It is within Humboldt-Toiyabe National Forest. It is 11.7 miles long and begins at 5,885 feet altitude. Traveling the entire trail is 23.5 miles with a total elevation gain of 2,742 feet. The Big Crystal Mine (elevation 6,506 feet) quarry can be seen along the trail.