Viscous jeweller's glue and construction adhesive will attach stones together permanently -- jeweller's glue for small jobs, adhesive for larger stones. Both adhesives are waterproof. If you'd like the option of easily separating the stones later, use hot glue.
Transfer a small amount of viscous jeweller's glue or waterproof construction adhesive from the tube onto a section of each stone with a toothpick or craft stick.
Wait at least one minute for the glue to activate. Press the glued areas on the stones together. Remove any glue that extrudes beyond the joined area with a toothpick or a craft stick.
Wrap a strip of painter's tape tightly around small stones. Attach a clamp to apply pressure to large stones. Leave the stones undisturbed for at least 24 hours while the viscous glue dries.
Insert a glue stick into a glue gun and plug in the gun. Set it on a piece of cardboard or some other protective, disposable surface to protect your work surface from dripping hot glue.
Apply a small amount of hot glue to your stone where you want to join it with another.
Press the second stone onto the hot glue. Hold the stones together for one minute while the hot glue hardens.
Apply glue in a well-ventilated area.