You may have seen tiny crystals on the cork or at the bottom of a wine bottle and wondered what they were. Rather than being anything to worry about they are actually a sign of an extremely good wine maker and a high quality wine which is rich in minerals. The crystals are sometimes known as "Weinsteine".
Riper grapes have higher levels of tartaric acid. The longer grapes ripen on the vine, the longer they have to absorb minerals from the soil. Little by little crystals can develop when these minerals come into contact with tartaric acid. Rather than dissolving in the wine, they precipitate and form a deposit on the sides or bottom of the bottle, on the cork, or on the inside of the barrel.
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