What if we used just enough ferrous metal as a kernel inside a grown crystal of garnet that the metal is sufficient to magnetically levitate the grain of abrasive; perhaps even extremely fine metal dust embedded within the grown crystal's matrix. Then could we pass the resulting metal-enhanced garnet abrasive grains through a Gatling rail gun?

Furthermore, since garnet has specific refractive properties different from other materials, could we pass all ferrous grains through an extremely high-speed discriminating chamber that looks for these properties in each grain, and magnetically directs the garnet grains back to the abrasive holding bin to vastly increase the recycling, while all other ferrous material goes a separate bin (for waste or other recycling purposes)?

I kind of wonder what problem this would be solving? It sounds magnificently cool, but also expensive. In the long run, I have great hope for fiber lasers becoming cheap enough for a home-version. Maybe a home-grade 1kw. Seems more practical than worrying about recycling sand.

I do love the idea of a Rail gun cutter, though - just not sure how it could really help cut things.

I'm thinking in terms of resource-constrained use cases, like on an aircraft carrier or further out, deep space exploration. Until this thread, I had always assumed a laser cutter would be just as good, but didn't realize some of the unique advantages of a waterjet cutter.