septarium

noun, plural sep·tar·i·a [sep-tair-ee-uh] /sɛpˈtɛər i ə/. Geology.

1. a concretionary nodule or mass, usually of calcium carbonate or of argillaceous carbonate of iron, traversed within by a network of cracks filled with calcite and other minerals.

noun plural -ia (-ɪə)

1. a mass of mineral substance having cracks filled with another mineral, esp calcite