The almost mythical soil type is a quite rare type of metamorphic rock that stems from another rock type called shale (it is also where slate comes from). If buried and subjected to very high temperatures over millions of years, shale gradually becomes slate. At that point, it is either pushed back towards earth’s surface or pushed further into the earth and stays there for even more millions of years eventually transforming into schist.

In the Douro, the soil consists of a mix of these different metamorphic rocks that got shifted from its horizontal alignment to an almost completely vertical one. The fragile rocks and the vertical alignment allows some vines to go as deep as 10 meters into the ground where deposits of water make it possible for the vines to survive the sometimes intense summer periods. This helps wine from this region keep their freshness while reaching great maturity!

This unique vertical soil composition is found in the Douro, the northern part of Portugal, in some places of Galicia and in select parts of Catalunya and the south of France. But you will also find schist, although not aligned vertically, in regions like the Rhône Valley, Beaujolais and Barolo.