A basic principle of antique renovation is that whatever you do, a future generation must be able to undo. So do not use superglue!!
Generally, gemstones are held in with claws and only a jeweller can re-make ("re-tip") broken claws. However, pastes (and especially marquisates) are glued, and jeweller's cement is especially designed for this. Non-drip (it's a 'gel' rather than a liquid), easy to handle, and you can remove the stones at a future date should the jewellery need repairing (lever the stone out, scrape away the residue of gel).
Mixing: no mixing required.
Application: use any fine point to apply, I recommend a cocktail stick or toothpick
Setting time: 24 hours
Apply with any fine point, a small paperclip will do, I find a cocktail stick or toothpick is easier.
As with all equipment and materials supplied by QUICKTEST, adhesives must be used in conjunction with the user's skill and experience. Under no circumstances shall Quicktest be liable for direct or indirect loss sustained in connection with any product.