Most igneous rocks at the surface are leucite-tephrites, with subordinate phonolites, limburgites, and olivine-nephelinites (at the Limberg Mountain near Sasbach), the last of which is rich in xenoliths from the Earth’s mantle. Carbonatite ignimbrite and lapilli are local peculiarities; they can be found in places in the western part of the Kaiserstuhl (Henkenberg near Burkheim, Kirchberg near Oberrotweil). 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. Minerals For a long time the Kaiserstuhl has been known for rare minerals. Examples include the quarries at the Limberg (zeolites), Badberg (carbonatites), Orberg and Fohberg. Well-crystallized minerals can be found predominantly in clefts or cavities in the volcanic rock. Loess The Kaiserstuhl is today largely covered by a Quaternary loess layer, a loosely cemented sediment. It is derived from other rocks through erosion and is then transported by the wind. The loess at the Kaiserstuhl – as in all the peripheral areas of the Upper Rhine Valley – was formed during the last Ice Age. Large parts were bare of vegetation and so loess was winnowed out from the Rhine sediments. It was then deposited in the periglacial area (i.e. ice-free, but surrounded by glaciers) at the Kaiserstuhl. The major process active here was frost weathering resulting in crushed rocks. The wind blew strongly, as there was no vegetation that