![]() The purest varieties contain up to 99 percent calcium carbonate in the form of the mineral calcite. Chalk is composed of the shells of such minute marine organisms as foraminifera, coccoliths, and rhabdoliths. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!Ĭhalk, soft, fine-grained, easily pulverized, white-to-grayish variety of limestone.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |