Can anyone tell me what this rock is called?

[fireman1173005]

Wondering if anyone can tell me what this type of rock is called. Wanting to call around and get some prices on it but I live about an hour from the closest place that would sell something like this so if you could help me out with a name I'd appreciate it. Thinking about making a flower bed out of something like it and using mortar to hold it together. Would anyone recommend using a concrete or motor base or just setting it on flat solid dirt?

Brian