Roundness (geology)

Sphericity is a measure of how closely the shape of a physical object resembles that of a perfect sphere. For example, the sphericity of the balls inside a ball bearing determines the quality of the bearing, such as the load it can bear or the speed at which it can turn without failing. Sphericity is a specific example of a compactness measure of a shape.

Sphericity applies in three dimensions; its analogue in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft, is called roundness.

Breccia (/ˈbrɛ(t)ʃiə/ BRETCH-ee-ə, BRESH-; Italian: [ˈbrettʃa]; Italian for 'breach') is a clastic rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.

The word has its origins in the Italian language, in which it means 'rubble'. A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, fault or tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia.