I usually don't take photos of the rough gem material. However, because I had a few questions about what it looks like before it is faceted, I did remember one day to get some pictures of parcels I had recently acquired. Now that I have cut some of those pieces, I have a group of "before" and "after" pictures of few garnets.
Obviously in these photos, the scale is not consistent. However, you can see some typical rough garnet and what was done with it. Most of the garnet rough I have encountered is similar to water worn pebbles rather than a nice geometric crystal.
In some cases, a very fine saw may be used to split the material or remove excess material. However, the bulk of the faceting work is done by grinding off the excess to create each facet of the gem. The faceting process involves first removing flaws in the material and shaping the stone with a coarse grit. Then with a finer grit, each of the facets is cut. Often a very fine grit is used to produce a "prepolish" on the facets. Then each facet is polished with an extremely fine grit or an oxide to produce essentially a mirror finish. It is not unusual for two thirds or more of the original rough material to end up as sludge in the bottom of the splash pan of the faceting machine.
Most faceters in the US try to do precision cutting -- angles chosen are to maximize the light return and all facets properly shaped meeting its neighbors exactly according to a predetermined pattern. Another approach to faceting is what is often labeled "native cut". In that case, the material is cut to maximize the weight of the finished stone, often at the expense of the brilliance. The facets on native cut stones also tend not to meet nicely, they are misshaped and do not line up with each other. One other major difference between "native cut" and precision cut, is the polish.