Hematite Processing Site
12 bedrock mortars at Holy Names College.
Hematite was processed and quarried here. It was often burned, which produced brighter reds, and then leached to remove salts and soften the rock. After that it was ground to a powder.
Closeup of a chunk of hematite. Subtle processing differences produced different hues of red ochre.
This may not have been the only hematite processing site in the area. William J. Wallace in “An Aboriginal Hematite Quarry in Oakland, California,” American Antiquity, Vol. 12, No. 4, (Apr. 1947), pp. 272-3 describes an outcrop of Hematite at the intersection of Redwood Road and Mountain Boulevard used as a quarry and processing center. His description of that site is sufficiently different from the Holy Names site to suggest that Wallace’s site was obliterated by the Warren Freeway (State Highway 13). Further research is necessary here.