What is this?

I opened a bottle of wine and there was what looked like salt or something mineral like all over the cork and the top inside of the bottle. Is this a common occurance?

[James Roscoe]

Yep. The wine should be fine. I forget what they are called. One of the elder statesmen will tell you.

Potassium tartrate crystals (also known as cream of tartar). It's perfectly normal and harmless. If anything it's a good sign that the wine has adequate acidity, and that it wasn't overly manipulated before bottling. Some wineries cold-stabilize (read: nearly freeze) their wine to force the crystals to precipitate out before bottling, then filter them out, so as not to unduly alarm uninformed consumers.

-Paul W.

...Some wineries cold-stabilize (read: nearly freeze) their wine to force the crystals to precipitate out before bottling, then filter them out, so as not to unduly alarm uninformed consumers.
-Paul W.

Actually, you are partly correct. Cold stabilization precipitates out the crystals. However, if this is not done, when the wine is chilled, it will become cloudy from the crystals falling out of solution. Most reds are not cold stabilized, while most whites are.

[James Roscoe]

Tina, I knew that you would get good answers from this group. It's like magic!

[David M. Bueker]

Wine Diamonds! A sure sign of superior quality!

...Some wineries cold-stabilize (read: nearly freeze) their wine to force the crystals to precipitate out before bottling, then filter them out, so as not to unduly alarm uninformed consumers.
-Paul W.

Actually, you are partly correct. Cold stabilization precipitates out the crystals. However, if this is not done, when the wine is chilled, it will become cloudy from the crystals falling out of solution. Most reds are not cold stabilized, while most whites are.

Not an elder statesman, but to elucidate. When the grapes come in, there is an equilibrium solution of potassium bitartrate in the juice. As the wine ferments, alcohol is produced. The solubility of potassium bitartrate in an alcohol solution is less than in a water solution, so the potassium bitartrate exists in a super-saturated state in the alcohol-containing wine. It will slowly precipitate out of solution. To hasten this process, primarily for white wines that are not aged so long, they can cold-stabilize...which means putting the wine in a tank and dropping the temperature to near freezing..which accelerates the precipitation process. They then do a light filter to take the potassium bitartrate out of the wine. Actually..a pretty harmless process. If they do not cold-stabilize..the potassium bitartrate will naturally precipitate out, often on the cork (where there are more nucleation sites) and then may fall to the bottom of the btl. They are harmless and tasteless (like a lot of the folks around here)...just a little crunchy is all.
The same situation exists in red wine (supersaturated solution of KBiT), but red wine in normally aged longer in the wnry and the KBiT will naturally precipitate out, so cold stabilization is seldom needed for reds...unless it's a Gamay or something that's bttld early. If you take a look-see in a long-used big oak or redwood tank/oval for red wines (like at Fillipi or Thomas wnry, where they still have a bunch), you'll see the inside of the tank coated with these KBiT crystals. In fact, back in the olden days, back around WWII, back when Howie was in his prime, back afore my time, wineries were the most common source of cream of tartar. Now there are more practical/cheaper, less natural, sources of cream of tartar.
Waaaay more than you wanted to know, probably, Tina.
Tom

A vineyard near my home (one of 4, I'm happy to say) actually takes their abundance of Potassium tartrate left over from the wine making process and gives them to local institutions who have a need for them. I use them to polish metal alloy wheels.

A vineyard near my home (one of 4, I'm happy to say) actually takes their abundance of Potassium tartrate left over from the wine making process and gives them to local institutions who have a need for them. I use them to polish metal alloy wheels.

Jon,

You can make gun powder from it...