| Name | Septaria (or Septarian) |
| Class | Sedimentary concretion with a predominantly carbonate composition |
| Category | Septarian nodule composed of several minerals |
| Crystal system | Variable depending on the minerals: trigonal (calcite) and orthorhombic (aragonite) |
| Chemical composition | Mainly calcite and aragonite (CaCO₃), associated with a clay-limestone matrix. Barite, quartz and pyrite may also be present. |
| Hardness (Mohs scale) | Approximately 3 to 4 for the carbonate constituents, varying according to the composition of the matrix |
| Transparency | Opaque, with some translucent calcite veins |
| Geographical origin | Madagascar (Mahajanga region), United States (Utah), Morocco, United Kingdom and New Zealand |
