In geology, a placer deposit is a deposit of earth, sand, or gravel, containing valuable minerals in particles, especially by the side of a river, or in the bed of a mountain stream. Placers may also be found at the oceanside, deposited by the action of waves. Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ...

Placer mining is an important source of gold, and was the main technique used in the early years of the California gold rush. The name is from the Spanish word placer, meaning "pleasure", because placer mining is much easier than pick-and-shovel mining. A sluice box used in placer mining Placer mining (pronounced plass-er) is a open-pit or open-cast form of mining by which certain valuable minerals are extracted from the earth without tunneling. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... Gold rush handbill The California Gold Rush was a period in American history marked by mass hysteria concerning a gold discovery in Northern California. ...

Placer deposits form due to the differential settling of the denser, heavier components of moving sand and gravel. Placer materials must be both dense, and resistant to weathering processes.

Notably, placer environments typically contain black sand, a conspicuous shiny black mixture of iron oxides, mostly magnetite with variable ilmenite and hematite components. Accessory minerals often occurring with black sands are monazite, rutile, zircon, chromite, wolframite, and cassiterite. Black sand is a heavy, weakly magnetic, glossy, semi-metallic mixture of usually fine sands, found as part of a placer deposit. ... Magnetite is a ferromagnetic mineral form of iron(II,III) oxide, with chemical formula , one of several iron oxides and a member of the spinel group. ... Ilmenite (FeTiO3) is a weakly magnetic iron-black or steel-gray mineral found in metamorphic and plutonic igneous rocks. ... Hematite (AE) or haematite (BE) is the mineral form of Iron (III) oxide, (Fe2O3), one of several iron oxides. ... Monazite powder In geology, the mineral monazite is a reddish-brown phosphate containing rare earth metals and an important source of thorium, lanthanum, and cerium. ... Rutile in trellis texture characteristic of secondary rutile. ... Zircon dust Zircon is a mineral belonging to the group of nesosilicates. ... Chromite, iron magnesium chromium oxide: (Fe,Mg)Cr2O4, is an oxide mineral belonging to the spinel group. ... Wolframite (Fe,Mn)WO4, is an iron manganese tungstate mineral that is the intermediate between ferberite (Fe2+ rich) and huebernite (Mn2+ rich). ... Cassiterite is a tin oxide mineral, SnO2. ...

There are heavy silicates, such as amphibole and pyroxene, that will collect in extensive placers where they comprise the country rock. Of course, exceptionally dense substances like gold and the platinum group members will accumulate in placers, when they are present. In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... For the logical fallacy, see Amphibology. ... The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... The platinum group or platinum family is a group of six metal elements with similar physical and chemical properties. ...