Not everyone can convincingly compare a soil type to a classic French dessert, but Thierry Fritsch sees the sweetness in schist.
Comprised of flaky layers of rocks and minerals, shist is “sort of a mille-feuille baked at high pressure in the depths of the earth’s crust,” says Fritsch, head oenologist and chief wine educator for Conseil Interprofessionnel des Vins d’Alsace, a wine organization in Alsace, France.
Like slate, schist is a metamorphic soil, meaning it formed when an intense bout of heat and pressure transformed one type of rock into another. Its fine-grained, crystalline character has pluses and minuses for winemakers.
Schist is “resistant to weathering and erosion, and often produces very prominent terroirs,” says Jordi Vidal, wine director for ThinkFoodGroup.
It also retains heat well and has good drainage. These characteristics are useful for growers in hilly Alsace or those cultivating indigenous Carignan and Garnacha grapes in mountainous Priorat, Spain.
“Both these grape varietals need plenty of sunshine and heat to thrive, and the steep, mainly schist soils of Priorat are excellent for retaining both the heat and the very scarce and much-needed water,” says Michael Evans, CEO of The Vines, a global network of vineyards.
In search of water, the grapevines’ roots descend into schist’s rocky layers.
“Fractured, laminated schist allows the vine roots to penetrate the cracks down as far as seven or eight meters deep, where rainwater naturally flows,” says Fritsch.
This deep dive has benefits beyond hydration.
“On the way, the roots absorb lots of minerals, which is known to give low yields of small grapes with thick skins but a high concentration of flavors, color, acidity and tannins,” says Evans. “The result is highly intense and aromatic, often big and bold, depending on the winemaker, but always with a lot of what we call ‘mineral’ notes.”