stylistic:tone
Types

Breccia is composed of coarse rock fragments held together by cement or a fine-grained matrix. Like conglomerate, breccia contains at least 30 percent of gravel -sized particles (particles over 2mm in size), but it is distinguished from conglomerate because the rock fragments have sharp edges that have not been worn down. These indicate that the gravel was deposited very close to its source area, since otherwise the edges would have been rounded during transport. Most of the rounding of rock fragments takes place within the first few kilometers of transport, though complete rounding of pebbles of very hard rock may take up to 300 kilometers (190 mi) of river transport.

A megabreccia is a breccia containing very large rock fragments, from at least a meter in size to greater than 400 meters. In some cases, the clasts are so large that the brecciated nature of the rock is not obvious. Megabreccias can be formed by landslides, impact events, or caldera collapse.

Breccias are further classified by their mechanism of formation.