Located at Hallelujah Junction, California, the Petersen Mountain quartz diggings is a well-known rockhound location where one can collect excellent quartz crystals, including amethyst & smoky quartz.  While sifting the loose top soil, one will usually get a few quartz points, however the real prize is finding a quartz scepter which is less common.  Rock collecting is done in both California & Nevada however there is more private land on the Nevada side, plus a private commercial mine is located at the top of the mountain.  I happened to find one light smoky scepter after an hour of digging around leftover pits, but may look to other areas for potential finds.