The subvolcanic and intrusive rocks of the central Kaiserstuhl are plutonic equivalents of the erupted material (essexite, carbonatite and coarse-granular phonolite). Several local terms which do not carry official status with the International Union of Geological Sciences have been used for different varieties of the intrusive rocks. Of major scientific interest is the consolidated carbonatite near Altvogtsburg und Schelingen. It is a quite rare volcanic rock, which crystallized from a carbonate magmatic melt rather than a silicate one. Given its unusual composition for an igneous rock, the magmatic nature of the carbonatite was not proposed for a long time and remained doubtful subsequently. An alternative interpretation was that it was a metamorphically altered sedimentary rock, examples of which can be found nearby. Only in the 1950s and 1960s did research prove that it was a carbonatite; one of the clues was identification of the eruptive carbonatites found in the western part of the Kaiserstuhl. The carbonatite contains the niobium rich pyrochlore; attempts to mine the carbonatite rock for niobium were carried out in the middle of the 20th century, but the amount turned out to be too small to be economical.