Procedural Flagstone Material 

UVs required: YES
Render Engine: CYCLES
Displacement: YES

If you want to save processing time and use BUMP instead of Displacement
You can switch the Displacement Method to Bump Only in the Material Settings:

How to use Mapping node with this material

Material Artist: Sanctus

This material is also sold as part of the Sanctus Library addon

along with hundreds of other materials.

You can also check other materials I made here

How to use the material

You can append the material to your scene by going to File>Append... navigate to the downloaded blend file containing the material, double click it, double click the Material folder, select the material and click the Append button. Once done you will be able to assign it to your object in your scene.