According to records, the Rocklin quarries produced Bitotite Granite which is the light grey rock with black specks.
Principal granite-producing point in the Sacramento Valley. First quarry opened in 1863, stone used in construction of the Southern Pacific Railroad. Stone used in construction of the State Capitol in Sacramento, Hibernia Bank and Crocker building, San Francisco. Rocklin quarries lie close together in area less than a mile square on "gently rolling plan.Granite occurs at the surface in most cases. Rocklin stone is biotite granite. Contains some plagioclase and a little augite, but the prevailing feldspar is orthoclase, and biotite is in excess of muscovite." Fifteen quarries in operation in 1904, several idle. Most were small and operated by Finns, Russians, and Italians. Largest and most northerly situated owned by Rocklin Granite Co., ".a rectangular pit, sunk in surface of the rolling plain. The opening is about 100 feet deep, 100 feet wide, and 250 feet long.."
