Nearly all sediment found in wine is naturally occurring and is in no way harmful.
In fact, many wine pros and enthusiasts like to see a bit of sediment in their wines, particularly red wines that have been in bottle for more than five years. Sediment in wine can indicate a wine that has not been heavily filtered or otherwise processed.
Sediment is a part of wine making. At the bottom of every fermenter you will find a layer of sediment comprised of dead yeast cells, grape parts, tartrates, pigment polymers, and other disagreed solids.
When a wine ages in cask many of these same items fall from the wine over time and are separated from the clear wine before bottling.
Once a wine is in bottle it may develop fine solids that become sediment over time as the wine ages (even when the wine is perfectly clear at bottling). You will rarely see sediment in wines younger than five years and fairly common in red wines aged 10 years or more.
Sediment found in bottles of wine include polysaccharides, proteins, pigment, and tartrates (potassium bitartrate crystals). Tartrates when collected in tank and barrel at the winery can be collected, sold, and processed into cream of tartar, which is a common kitchen item known to most any baker.
While sediment in your wine is totally harmless, few people want a mouthful of chunkies while sipping their wine. You can avoid most sediment by decanting the wine carefully leaving most of the solids in the bottle. See our story on Decanting Wine.