At an elevation of 4,965 feet above sea level, its summit rises 965 feet above nearby Little San Jacinto Creek. San Jacinto Mountain is an intrusion of volcanic basalt and rhyolite surrounded by sedimentary deposits of sandstones and conglomerates in the Alamito Creek valley. The topography of the area is desert mountain terrain and rugged canyon land with loose surface rubble.
Vegetation consists primarily of sparse grasses, cacti, and desert shrubs of conifers and oaks.
The Texas State Historical Association, 1997,1998,1999.