- Mt. Persis is Mt. Index’s little sister. One might say Persis is Index’s stunted twin, for the two peaks share a lot of “facial features.” Both are steep walled on the north and east sides and both are rugged but relenting on their south and west sides. This is understandable, as both peaks are part of a granodiorite intrusion emplaced in the early Tertiary Period (50-60 million years ago).
