This document contains descriptions of different rock specimens collected by the author in various locations in California and Hawaii. It provides details on where each rock was found and background information about the formation of obsidian, marble, sandstone, granite, and muscovite schist. The author notes finding obsidian near a waterfall in Hawaii, marble in Three Rivers, sandstone in caves at Pismo Beach, granite in a park near Three Rivers, and muscovite schist alongside a mountain road between Lemon Cove and Three Rivers.