This video shows you how to set a Herkimer Diamond into Huggie Prong Earring stud component. (You can set it free hand, but I am using a watch maker tool that has a hole long enough for the post. You can also use a vise or drill a small hole into a block of wood. The idea of the tool is to free a hand and hold the prong setting in place).
Once you have decided how the Herkimer Diamond – or whatever you wish to set – is to sit, hold the Diamond down in place. Using the side of a pair of pliers or metal object, push each prong closer around the Diamond, starting from the bottom. (You can use your fingers, but as you make more of these, your fingers can become sore. It is easier to use a hard tool to help you save your fingers!). It is best work on each prong a little bit, rotating them, so that they are evenly tightened while the stone is kept in place.
After you have closed the prongs, almost completely, trim the prongs as you wish. Often the Herkimer Diamonds and pebbles are irregular in shape and you have prongs that seem shorter. The final trim makes them visually even and attractive. You can then file the prongs to a point, by filing the sides, or rounded before the final closing.