Santa Clara County. Los Gatos is in the foothills of the Santa Cruz Mountains. Bordered by San Jose, Almaden Valley, and Saratoga.
A lot of counties have online access to property deeds. I'm guessing you could check your parents deed to see of the mineral rights had been removed. I'm guessing that the mineral rights would have to be on record down at the courthouse. Some counties have all their records online.
My .02 .