Ever notice crystals that look like shards of glass adhered to the bottom of an extracted wine cork, sitting on the bottom of the bottle or actually in your glass when poured? Well, they are not. Better known as “wine diamonds”, these are tartrate crystals mostly made up of potassium bitartrate. These mineral precipitates which separate from the wine usually form during ageing in tank and or in the bottle if the wine is subjected to cold temperatures. Cold stabilization can cause this too. Don’t worry, they are perfectly harmless and won’t hurt you should you ingest them, but they look weird. Simply decant the wine off of them. However, many consumers, thinking they’re glass bits, return the wine to the retailer with complaints.