I have a deposit at the bottom of my bottle, why?
A deposit of crystalline appearance can sometimes occur in the wine: it is tartar that is deposited under the action of cold.
This deposit is perfectly natural, the tartar comes from the grapes.
It does not alter the taste of the wine.
It does not present a risk for the consumer.

A deposit of tartar in the bottle is perfectly natural.
The shoulder of the bottle avoids pouring it into the glass.
Most of the time, tartar is removed by successive rackings during the maturing of the wine, but it may remain in solution in the wine at the time of bottling.
Under the action of the cold (for example during transport), a crystalline deposit forms in the bottle.
This deposit in no way alters the quality of the wine, just be careful when serving the last glass.
You can also serve it in a carafe: this also causes a light aeration, which is generally favourable to the development of the aromas.
Here are some articles in the blog that talk about tartar in wine :
Le tartre tapisse les parois des cuves
Mannostab, un apport récent de la recherche oenologique
Here are also corresponding wikipedia articles: