Black Basalt Rock Dust (High Calcium Magnesium) NEW! Dr Greenthumbs
pH, Silica 43%, Calcium 7%, Magnesium 14%, Potassium %, Iron 14%, Manganese %. Our Black Basalt rock dust is largely made up of the mineral olivine. It is a silicate mineral often found in basalt and peridotite, two volcanic rocks. Olivine is also found in meteorites. The most typical source of olivine rock dust is volcanic deposits.