What is Calcareous Clay?
Many vineyard sites, especially the top tier french chateaux and domaines, describe their soil type as calcareous clay. Calcareous is actually an adjective meaning "mostly or partly composed of calcium carbonate." Other synonyms for calcium carbonate include lime or chalk. Due to the low acidity level of calcium carbonate, the calcareous clay soil is quite alkaline compared to other soil types. The biggest benefits of calcareous soil are the special nutrients it supplies to the grapes, which make them grow better and sweeter. It also has the effect of keeping the soil at a cooler temperature, which can be helpful on hot days, but it also usually delays ripening, yielding a more acidic wine. The clay portion of the soil retains moisture, which helps the grapes during dry weather.