Active gold placers include the Browns Gulch placer and the Confederate Gulch placer. California hydraulic mining exploited gravel deposits, making it a form of placer mining. Placer deposits were mined out by 1867. The simplest technique to extract gold from placer ore is panning. Badakhshan Province also had occurrences of placer gold deposits. John McTeague is a miner working in Placer County, California. The miners prospected far and wide for new placer gold discoveries. Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes. In placer mines, the gold is recovered by gravity separation. The basic concept of retrieving gold via placer mining has not changed since antiquity. In 1860, he moved to Camptonville, a center of placer mining activity. These metals occur associated with ultramafic intrusions and placer deposits derived from those intrusions. Olympic Valley is an unincorporated area located in Placer County, California. It is often found in placer deposits. The river sand garnet occurs as a placer deposit.