Breccia pipe

Breccia is typically silicified and consists of many smaller irregular rock fragments.
Breccia pipe cutting Eday Sandstone, Ophir Bay, Orkney

A breccia pipe, also referred to as a chimney, is a mass of breccia (rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix), often in an irregular and cylindrical shape.[1]

  1. ^ "Glossary of Meteoritical Terms". New England Meteoritical Services. Archived from the original on December 25, 2001. Retrieved August 10, 2019.