A concretionary nodule, typically of ironstone, having radial cracks filled with calcite or another mineral.
- ‘Iron oxide nodules are commonly septaria, exhibiting networks of thin veins of coarsely granular calcite.’
- ‘Phosphatic nodules, large dolostone septaria, iron sulfide nodules, and crystal-lined vugs are present.’
- ‘Large dolostone septaria and iron sulfide nodules occur in the Late Devonian Huron Shale.’
- ‘Matrix minerals of the dolostone septaria are ferroan dolomite, quartz, calcite, and pyrite.’
- ‘Dolostone septaria and iron sulfide nodules occur in the Late Devonian Huron Shale.’
Late 18th century: modern Latin, from Latin septum enclosure.