From http://beer-pages.com/glossary/glossary_q_z.htm
RAUCHENFELS STEINBIERE
Rauchenfels brewery, Germany. This brewery revived the concept of "stone-beer", which harked from times prior to the development of metal kettles, when huge baking-hot stones were heated and dropped in to heat up the wort, which in its wooden vessel could not be boiled by direct heat. The result (in the version brewed by Rauchenfels today, anyway) is a smooth, rich-tasting beer with a curious, smoky-caramelised aftertaste. A "stone-beer" has an acquired taste, which the cult-following of Rauchenfels has obviously acquired.
RAUCHENFELS STEINWEIZEN
Rauchenfels brewery, Germany. The wheat beer version of "stone-beer", Steinweisen is predictably sharper taste and is preferred by Rauchenfels cult-following.