Breccia forms when shards of rock, over at least 0.08 inches in length, are cemented together a relatively short distance from where they were originally broken off. Often this occurs at the base of an outcrop of rock where mechanical weathering occurs.
Breccia is a sedimentary rock where sharp, angular pieces of other rocks are stuck together. They can be bound together with either a mineral cement or a mix of smaller rock fragments. It is very similar to conglomerate, except conglomerate contains rounded pieces of rock instead of angular ones. Breccia constituents are sharp because they are not carried a great distance before becoming embedded in sediment. Otherwise, the edges would be worn down.
Breccia has no particular mineral composition, and is a term for any sedimentary rock matching its physical description. They are often a mix of different minerals, but if one type of mineral predominates, it can be called limestone breccia, granite breccia or whatever name best characterizes the source rock. Because of the variety of mineral compositions, the color and general appearance of breccias vary widely. There are few human uses for breccias, although the breccias from certain private quarries are used for various decorative applications.