Have you ever found when you opened a bottle that the area of the cork that was in contact with the wine shone? That it had small crystal deposits attached to the cork? This phenomenon is called “wine diamonds”.
If you have ever come across these crystallisations when opening a bottle of red wine, don’t panic, these crystals do not affect the quality of the wine. So-called wine diamonds are known chemically speaking as potassium or calcium bitartrate. They are formed when tartaric acid, a natural component found in grapes, binds with the aforementioned cations in cold conditions and a lot of movement, such as sea waves, and forms a crystalline salt that binds to the cork.
Some varietals, such as Tempranillo, are highly charged, so they are prone to tartaric precipitation and therefore, diamonds.In any case, these crystals are not harmful either for the consumer or for the quality of the wine and their appearance simply indicates that they are a natural product that comes from the fruit of the vine.