placerite

Placerite is an informal term used in geology and mining to describe the heavy-mineral concentrates recovered from placer deposits, such as stream, river, or coastal deposits. It is not an officially recognized mineral species and does not have a defined chemical formula or crystal structure. In most modern references, placerite is treated as a descriptive material—the mixture of minerals obtained from placer mining—rather than a single mineral.

In placer environments, the processing and transport of sediment by water lead to sorting by density. Dense minerals tend to accumulate in placer concentrates, while lighter minerals like quartz are removed or dispersed. The composition of placerite is highly variable and depends on the provenance of the sediment and the conditions of deposition. Common constituents in heavy-mineral placers include gold in gold-bearing deposits; magnetite, ilmenite, zircon, rutile; garnet; monazite; cassiterite; and other dense minerals. The exact mix can indicate the source rocks and geological history of the area.

Economic significance of placerite depends on its contents. When the concentrate contains valuable metals such as gold, platinum-group elements, or rare earth-bearing minerals, it becomes the target of mining and processing operations. In many contexts, however, the term placerite is superseded by more specific terminology, such as “placer concentrate,” or by identifying the minerals present.

See also: placer mining, heavy mineral sands, mineral concentrates.