Sediment at the bottom of the bottle

[Kcwhippet]

Those are potassium bitartrate crystals. Tartrates are naturally ocurring and they are completely harmless. They show up when a bottle of wine has been cooled down enough to cause the tartrate to precipitate out as crystals. A lot of wineries actually cool down their wines and remove the tartrates before bottling. They then sell the stuff which is cleaned up and ground into a powder, then sold in supermarkets as cream of tartar.