Sample of chalk, a sedimentary rock formed of calcite, a form of calcium carbonate. Chalk is formed by the gradual deposition of the shells of marine organisms over millennia. | |
Licence : | Droits gérés |
Crédit : | Science Photo Library / RHYS LEWIS & MINH TAN PHAM, AHS, DECD, UNISA |
Model Release : | Non requis |
Durée : | 33 Secondes |
Aspect ratio : | 16/9 |
Restrictions : | - |