Wine crystals
Wine crystals (Weinstein) that tend to form in finer wines, especially in good harvests, and which you may find on the cork or at the bottom of a bottle are not flaws.
Crystals
They are harmless, tasteless and in no way detract from the flavor of the wine. On the contrary, they are considered a sign of quality. Nevertheless many of Germany's white wines are treated to cold stabilization before being bottled. This is the process of storing wine in below-freezing temperatures in order to eliminate the tartaric crystals.