Jagged Lists (nested List ) performance

I am designing a game, and I need to keep track of a 3d list of geometry chunks. Before I build upon this, I would like to know about performance and such with using nested List<T>

Example:

public List<List<List<Chunk>>> Chunks;
int x=0,y=0,z=0;
Chunks[x][y][z].SomeProperty = 0;

I am concerned with lookup speed, and drawbacks. When the world gets to be lets say 10K chunks in size, is this method really the best approach?

---

(=Chris=)