Crystals in the bottle of wine.

[Ted mlodzinski]

After opening 2 bottles of Mouton-cadet whitesmall crystals fromed in the bottom of the bottle. The wine did not lose any flavor but the crystals did not look appealing to the eye.

[Bucko]

Harmless tartrate crystals - many wines (Kistler Chard as an example) often have them.

Bucko

[Thomas]

The crystals mean that in the winemaking process the wine was not exposed to chilling long enough and at cool enough temperatures to throw off tartaric acid crystals.

That stuff in the wine is known as "cream of tartar". Harmless, unless used in gunpowder.