A representative sample from the Sespe formation, from the Upper Ojai valley, California, was examined as to its mineral content and the following minerals were found: quartz, feldspars, calcite, muscovite, epidote, lawsonite, garnet, zircon, glaucophane, cyanite, pyroxene, tremolite, serpentine, topaz, biotite, chromite, chlorite, spinel, rutile, monazite, tourmaline, hematite, limonite, and magnetite.

Most of these minerals are characteristic of metamorphic and granitic rocks and are strikingly similar to those which are typical of the Franciscan series. They suggest that the Sespe formation was largely derived from the Franciscan rocks and that the latter were probably widely exposed throughout the southern Coast Ranges during Sespe time. The freshness and angularity of most of the mineral grains indicates a short transportation and a lack of chemical weathering. These features point to the accumulation of the Sespe formation under continental conditions such as prevail during a semi-arid climate.