Roundness (geology)

[4][5] Experimental studies have shown that the angularity of sand-sized detrital quartz can remain virtually unchanged after hundreds of kilometers of fluvial transport.

The degree of roundness points to the range and mode of transport of clastic material, and can also serve as a search criterion in mineral exploration, especially for placer deposits.

Pebble dikes are dikelike bodies found in intrusive environments, usually associated with porphyry-type ore deposits, which contain variably rounded fragments in a finely-ground matrix of pulverized rock.

The clasts originate in deeper formations in hydrothermal systems, and have been brought up explosively by diatreme or intrusive breccias as groundwater and/or magmatic water flash boils.

Emmons, Central City, Leadville, and Ouray, Colorado; Butte, Montana; Silver Bell; and Bisbee, Arizona; and the Kiruna iron deposit in Sweden, Cuajone and Toquepala in Peru; El Salvador in Chile; Mt.

Rounded pebbles in a streambed
Well-rounded cobble from the beach on Teletskoe Lake , Altai Republic
Schematic representation of difference in grain shape. Two parameters are shown: sphericity (vertical) and rounding (horizontal).