If you are a habitual wine drinker, you are sure to have come across them from time to time. Tiny crystal formations at the bottom of your bottle or glass. They might be mistaken for broken glass or some other fault, but they are a Completely Natural part of winemaking. Technically they are even good for you.
Wine diamonds, or tartrate crystals are a natural deposit that one can find in wine, particularly in wine that has not undergone cold stabilisation (or one of the many alternative methods that can be used to remove tartrates). There are two main types of tartrates, potassium bitartrate and calcium tartrate.
Potassium bitartrate, which usually makes out the majority of tartrates in wine, also works as a dietary potassium, and wine is one of the riches natural sources of this salt. This is one of the biggest reasons that wine (in moderate amounts) can be considered healthy. Potassium, naturally occurring in wine, helps to balance our high sodium diet, by replacing the sodium in our body. Many people consume potassium chloride tablets to achieve the same effect, which by any measure could never be as pleasurable as drinking wine.
Consequently, it is a waste to remove tartrates from wine. But the last few decades it has become the norm, mainly because consumers have come to expect wine to be perfectly clear to the last drop, even if wine, by nature is a cloudy drink. And every intervention done, also comes with a cost, it removes some of the wines personality and brings up the final production cost. Which is a complete waste!
Therefore, the next time you come across wine diamonds in your bottle, be happy and accept them for what they are. There is no need to return the bottle or complain. Wine diamonds are a testament of low intervention, which is something good. So, drink and enjoy, and if you do not want to drink the crystals, just be careful when you pour, and you will be good.
Read Understanding Wine Technology by David Bird for more information