Dolomite is a  rare species at Limberg. The "Bitterspat"  mentioned by  Walchner (1823) and Eisenlohr (1829) may be Dolomite or Magnesite or both. Dolomite was again mentioned by Knop (1892)  but not  from Lorent (1933). Lorent gives a description of Magnesite as large, dense, white concretions  of considerable size. This was not found in the last decades, but  Dolomite has been found recently  (2005) in a Limburgite-boulder with many cavities lined with Phillipsite. A few of the cavities show also Dolomite as rosette like aggregates of small tabular crystals on the phillipsite. Some Dolomite is also present on a boulder with larger Faujasites-crystals from Quarry II.   Dolomite can be distinguished from Calcite by its much slower (almost not) dissolution in diluted Acetic Acid (5%) or Vinegar. Magnesite is not affected at all under this condition. The test is best done under the microscope with a calcite grain as reference.  The identification was confirmed by X-ray diffractometry  (Erich Keck, pers. comm.)