Definition - What does Schist mean?
Schist is a type of metaphoric rock that is formed from deposits at the mouths of rivers or the bottoms of standing bodies of water. It is made from a combination of clay soils and water minerals that metamorphose into shale and then to slate, eventually hardening into schist.
It takes hundreds of years for clay to eventually form into schist, but this rock is crystalized, and then pushed back up to the earth’s surface and eroded away to complete the rock cycle.
WineFrog explains Schist
Schists are known to have a rich amount of mica, graphite, chlorite and talc that causes its brittle or flaky texture as a soft rock. This type of rock is found in many soils that are used to grow vineyards because of the water-friendly properties and mineral rich composition that schist has. While it is not a great soil to build houses or structures on because of its softness, it makes a great soil for grapevines and other crops.
Some areas known to use schist in the grapevine cultivations are Portugal (the Douro Valley makes Port wine with schist soils), France (in Côte Rôtie), New Zealand (the Central Otago region), Argentina (Mendoza that makes Malbec and other rich reds) and Spain (in Priorat). The schist in these soils help to add minerals and to retain water, which expertly contributes to natural resources available and adds flavor to the wine. It is said that some of the wines made with schist soils also have higher amounts of antioxidants and resveratrol, which makes them healthier to drink.