Those perfectly round and shiny spheres don't naturally look perfect. They undergo a process to bring out their best appearances.
In order to create a sphere, a rough rock is turned into a sphere preform. A Preform is the preliminary shape of the rock, after it has been cut using a slab or trim saw. Preforming is the stage before grinding the material into its final form.
Creating a sphere preform can be done in couple ways.
First is the most common, where you use a slab saw and a 45-degree angle
jig to cut the edges of a rock until you get a near round shape. It requires at least 26 cuts. This method is time-consuming. And depending on the size of your rock, creating a preform in this way will take you a day to finish.
Second is using a core drill. This method is faster and will give you a more accurate preform. With a core drill, you can finish a preform in an hour, with only five cuts. The cleaner your preform, the faster you can perfect your sphere.
If you want to learn how to use a core drill in creating a sphere preform, watch this.