It is an effect called stone washing as it should resemble the effect on the stone washed jeans. Depending on the size and assortments of shapes and amounts of media a harder type media like ceramic works better. The thin oil is so less rusting rather than if a water based fluid is used.
With a smaller nozzled blaster and media and a light touch one could duplicate the soft bead blasted look.
It is also called matte effect in some circles.