Under the sea at the peak of the mountain
Overview: Fossil Mountain is a small peak about 1 mile east of the South Bass trailhead with plentiful remains of brachiopods, coral, mollusks, sea lillies, worms, and fish teeth forever entombed in the 250 million year old Kaibab Limestone that this peak is carved from. Getting there is an adventure in itself and is not recommended unless you are at the South Bass Trailhead for some other reason. Access to this area requires a minimum 1-hour drive on rough dirt roads, and there is a $25 toll to cross reservation land to get there. But if you are in the neighborhood anyway, it's a great way to spend a couple of hours.
Hike: Begin at Havasupai Point and follow the rim as it roller-coasters toward Fossil Mountain. The terrain is wooded but open, with soft, gravelly footing in many places. The views from the rim are spectacular and make the several steep climbs much more worthwhile. The saddle below Fossil Mountain is not much more than half a mile of hiking from Havasupai Point. You can alternately hike in a drainage a hundred yards or so south of the rim, but it is much less scenic and doesn't really offer any easier access.
At one of the roller-coaster saddles, you cross a narrow throat that offers a sheer drop into Serpentine canyon below. The west side is a gentle slope though, so you are not required to endure any unnecessary exposure. From the saddle below the peak, ascending to the peak is easiest to do directly along the ridge line. Staying to the left offers a more-difficult climb traversing against the fall line. As you go, take the time to look at the ground where numerous examples of fossilized remains are embedded in the limestone. The summit is only 315 feet up from the saddle and it only takes a few minutes to get there.
At the peak, the views of the western canyon are fantastic, from Serpentine Rapid along the Colorado to the northeast, Grand Scenic Divide and Huxley Terrace to the north, the Darwin Plateau and Mount Huethewali to the northwest, and the Esplanade to the west.
Because of the rolling terrain on this hike, you will gain as much elevation on your return to the trailhead as you did getting there. But the trip is no less scenic and viewing it from the reverse angle makes it seem like a different hike.
Access and Camping: As stated above, this is a very remote area and is difficult (and expensive) to get to. Most would agree it isn't "worth it" to make this hike unless you are in the area already. However if you are hiking from the Bass TH and have some time at the beginning or end of your trip, it is a worthy addition. Along the road to Havasupai Point, the historic Signal Hill Lookout tower still stands, though it is no longer open and the stairs to climb it have been removed. Camping is not allowed at Havasupai Point, but there are two designated car-camping sites along the 3-mile road between Bass and Havasupai Point. Both require a backcountry permit (Area SE9).
Caution: Hiking Fossil Mountain is cross-country. There is no trail. There is no source of water, and loose footing along the sheer cliff of the canyon rim can pose a hazard to those unfamiliar with off-trail hiking in the Grand Canyon. This hike should only be attempted by hikers experienced and comfortable with off-trail routes in the Grand Canyon and other desert locales.
Check out the Official Route and Triplogs.