Word Wednesday: Breccia

Welcome to Word Wednesday, Wolfstone Rock Shop’s weekly look at the language of rocks, minerals, and gems.

Breccia (BRET-chee-uh or BRESH-uh) is a rock composed of broken, angular fragments held together by a finer matrix or natural cement.

Angular pieces tell a story

Because the fragments remain sharp-edged rather than rounded, they usually were not transported far before being deposited or cemented. Compare this with conglomerate, whose rounded clasts generally experienced more tumbling and transport.

Many ways to make breccia

Breccia can form in fault zones, volcanic eruptions, landslides, cave collapse, sedimentary settings, meteorite impacts, and hydrothermal systems. Mineral-rich fluids may later fill spaces between fragments, creating striking patterns.

Collector tip

“Brecciated” material sold in the decorative-stone trade may be natural, stabilized, dyed, reconstructed, or assembled. Ask what the fragments and cement are, whether treatments were used, and where the material originated.

See this texture and other mineral features in person at Wolfstone Rock Shop, 1857 N Casaloma Dr, Appleton, WI 54913. Inventory changes often, so call (920) 809-8577 if you are looking for a particular example.