USGS EarthWord of the Week
Whether you pan for gold or rare earths, you’ll get a lot of sand...and this EarthWord!
EarthWords is an on-going series in which we shed some light on the complicated, often difficult-to-pronounce language of science. Think of us as your terminology tour-guides, and meet us back here every week for a new word!
The EarthWord: Placer
If you’re panning for gold, you’ve come to the right place-r, that is! Placers are a type of mineral deposit in which grains of a valuable mineral like gold or the rare earths are mixed with sand deposited by a river or glacier.
Placer is also a mining method term. Placer mining uses water and gravity to separate gold from surrounding material.
Placer is an Americanization of the Catalan word placel, which itself came from the Spanish word plaza, meaning “open space.”
Use/Significance in the Earth Science Community:
Placer deposits containing gold are areas that have highly concentrated accumulations due to stream/river erosional processes taking place around/over geologic terranes that contain gold, over a very long period of time.
Placer deposits are an important source of many valuable minerals, particularly gold and rare earth elements. They occur throughout the world.
USGS studies placer deposits as part of its Mineral Resources Program. From the 1890s Alaska Gold Rush (where 72% of the gold found came from placers) to modern-day rare earth deposits (of which quite a few are in placer deposits), USGS has placed an emphasis on studying these rich formations.
Hungry for some science, but you don’t have time for a full-course research plate? Then check out USGS Science Snippets, our snack-sized science series that focuses on the fun, weird, and fascinating stories of USGS science.