THE SUMMITS of the Taunus low mountain range consist of a hard rock called quartzite. The sandy sediments washed out of long gone mountain ranges were deposited near a coast during the Lower Devonian (about 400 million years ago). These deposits were soon compacted to form sandstone, which was subjected to high pressures when it became buried beneath thick layers of rocks. This resulted in a modification of the crystalline structure of the sandstone turning it into a hard quartzite. This was followed by a period of intense folding during the mountain building process when the Taunus mountain range was formed. The Taunus Quartzite contains more than 90% quartz (SiO2) and very little mica or feldspar. Therefore, the rock has a very low carbonate and iron oxide content. As a result, the soils derived from this quartzite have a very low plant nutrient content.
      Quartzite soils are debris soils. The weathering processes during the ice ages fractured the rock into large blocks. The grey-brown hortic anthrosol consists of quartzite gravel and boulders as well as slate. The proportion of stones is high so that the soil is only capable of storing small amounts of water. Deep ploughing has resulted in a friable soil with good rootability. The roots of the vine can easily penetrate to great depths on their quest for water and nutrients. This stony, sandy-silt soil is quick to warm and can retain the heat very well. Although the water reservoir in the topsoil is quickly depleted, the plants do not suffer from water stress. The vines find the water they need in the subsoil, where groundwater flows down the slope. The stoniness and high proportion of quartz in the fine earth fraction of this calcium carbonate-free soil means that the mineral nutrient content is low. Decalcified residual loess in the topsoil improves the water balance and nutrient supply. This moderately dry site warms quickly and promotes early ripening.