Don't know exactly what you're trying for but you can adjust the roughness setting in the reflective shader to .4 to .8 to get more dispersion of the light.
You could also turn off ray traced reflections in addition to boosting the roughness and see if you like that effect.
I added a second sunlight to try to match the example image you showed, it looks like it used a couple of lights at least.
This First image uses ray traced reflections, roughness setting of .5, refractive index 10. I place the reflective shader right after the sphere's default shader and set the color in the default shader to black.
Second image uses ray traced reflections, reflective roughness .5, ref. index 10, highlight intensity .7. I added a very tiny (all scales set to .001) power fractal to the displacement function of the sphere's default shader and set the displacement multiplier in the default shader function down to 0.001 to give the imported sphere a very tiny bump map for more difused effect.