To be fair I would look on google for some photo's of the type of stone your after, then unwrap the UV's then texture using photoshop by tileing the picture together, then using hte clone tool take away the seam's of the tiling and the repeating areas, then map this to the colour channel.

For the bump and spec I would then take the texture you just created and convert it to grayscale and map this to the appropiate nodes then play about with the settings to get the desired look.

Hope this helps you in some way