A chain or range of rocks lying at or near the surface of the water. See Coral reefs, under Coral.

A large vein of auriferous quartz; -- so called in Australia. Hence, any body of rock yielding valuable ore.

That part of a sail which is taken in or let out by means of the reef points, in order to adapt the size of the sail to the force of the wind.

To reduce the extent of (as a sail) by rolling or folding a certain portion of it and making it fast to the yard or spar.

is a mineral layer containing economic mineralization of interest; usually flat and tabular.

a gold-bearing sedimentary horizon, normally a conglomerate band, that may contain economic levels of gold.

A mineralised horizon containing economic levels of metal.

A layer precipitated within the Stillwater Layered Igneous Complex enriched in platinum group metal-bearing minerals, chalcopyrite, pyrrhotite, pentlandite, and other sulfide materials. The J-M Reef, which the company mines, occurs at a regular stratigraphic position within the Stillwater Complex. Note: this use of "reef" is uncommon and originated in South Africa where it is used to describe the PGM-bearing Merensky, UG2, and other similar layers in the Bushveld Complex.

A buildup of limestone formed by skeletal remains of marine organisms. It often makes an excellent reservoir for petroleum.

A type of reservoir composed of rock (usually limestone) formed from the skeletal remains of marine plants and animals.

a limestone formation that is usually under water or just above it

An ecosystem that sustains marine life.