Ben Lomond Quartz Diorite. Mentioned in discussion on geologic and geographic controls upon rate of solute erosion from coastal river basins between Half Moon Bay and Davenport. Water draining from the above quartz diorites are less mineralized than those draining from basins underlain by Tertiary sedimentary and igneous rocks. Age is Cretaceous.
[Notable exposures in coastal river basins between Half Moon Bay and Davenport, San Mateo and Santa Cruz Cos., western CA.]

Source: US geologic names lexicon (USGS Bull. 1350, p. 59).

Pg. 12-14, pl. 1. quartz diorite of Ben Lomond. (Cites G.W. Leo, 1967, California Div. Mines Geol. Spec. Rpt., no. 91, p. 27-43; available online https://archive.org/details/shortcontributio91cali.) Generally hypautomorphic-granular, but displays a variety of textures, ranging from a "clean" texture with near-euhedral hornblende and subhedral plagioclase to a "messy" texture with irregular dark minerals and few well-formed cyrstals. Some foliation is shown in thin section by orientation of dark minerals and quartz. Mapped in Ben Lomond Mountain area, west of Santa Cruz Mountains, central Coast Range, Santa Cruz County, western California. [Age is Cretaceous.]
[Ben Lomond Quartz Diorite of Baldwin (1967) not adopted by the USGS.]

Source: Publication.