Approach via the Ruby Lake trail. From Needleton, head upstream away from everyone else going to Chicago Basin. You'll pass through one meadow after 1/3 mile or so and enter another after an additional 1/3 mile. Looking around you may see several cut logs turned on end as chairs around a fire pit. You may also notice that the trail pretty much disappears. Head to the east side of the clearing and look for the Ruby trail. Look around hard if you don't find it at first. You want to make sure you find it. It's there. It's about 2-3 hours on a steep trail to the lake and another hour to the upper basin. The Index is easy to spot from the lake but much less obvious from higher up. From the upper basin, Animas Mountain is a large mess of blocks and towers to the north. Look for the largest gap between two rocky massifs with a small, triangular tower between creating something of a W shape. Do not head into this gully. Instead tend more west and climb into the next gully to climber's left. There is a large chockstone guarding the top of the gully that can either be tackled directly or easily (5.0) to the right. Once out of the gully, look uphill and the Index is the tallest of the three towers 200 feet above you. Head to the base of the shortest (left most) tower looking for a less than vertical hand crack and belay from there.