| Mineral class: | Carbonate |
| Composition: | Calcium carbonate, CaCO3 (same as calcite, but with a different crystal form) |
| Hardness: | 3.5 - 4 |
| Color: | Colorless, white, grey, yellow |
| Cleavage: | 1, indistinct |
| Crystal form: | Fibrous or needlelike |
| Environment: | Vein mineral, in cave deposits, or as pearly layer of shells |
| Comments: | Scratched by knife but not penny. Reacts with HCl. Candle flame makes powder. Alters to calcite. Named for the Aragon region of Spain. |