Here is a simple Marble MXM from your image.
You may have to adjust the Attenuation and/or Scattering Coefficient values (in the SSS BSDF) based on the final scale of the material as you intend to apply it (here is set for the Simball size).
If you want to get very fancy (or do closeups) you could make a bump/normal map for the cracks that are recessed – although this would require editing the texture in Photoshop (or a similar package), since most of the cracks are not recessed.
Best,
Jason.