Prism (geology)

In geology and petrology, a prism is a long, narrow, wedge-shaped sedimentary body with a width to thickness ratio greater than 5 to 1 but less than 50 to 1, and a length 1.5 to 3 times its width.

These types of sediments are typically formed during orogenic deformation. For example, the arkoses found in fault troughs.

"Prismatic" is also type of mineral habit (appearance of a crystal). Prismatic minerals have crystals that show a uniform cross-section.