Carbonatite (https://en.wikipedia.org/wiki/Carbonatite) from Magnet Cove alkaline igneous complex in Arkansas (https://pubs.usgs.gov/pp/0425/report.pdf; http://rockhoundingar.com/magcove.php). This sample from the WVU Petrology collection contains coarse- and fine-grained calcite (CaCO3), monticellite (CaMgSiO4; https://en.wikipedia.org/wiki/Monticellite), and perovskite (CaTiO3; https://en.wikipedia.org/wiki/Perovskite).