Artists, exactly what type of adhesive would you use to glue sea gl to an old coffee table top?

Clear 2 part epoxy glue is the best. It will dry hard and be permanent. Nothing will be able to get the gl off the table if you use epoxy. Also gel-type super glues will work. Don't use the liquid, it could damage the gl and the table and it's difficult to control. Gel type glue allows you to squeeze out a glob and place the gl on top of the blob and everything will stay in place. If you use super glue or epoxy be sure you don't get glue on the top of the sea gl or the gl will become cloudy. If you want the sea glass to be temporary so you can remove it some day then good old hot glue from the hot glue gun will work fine. it will hold the glass down and it won't damage the glass if and when you decide to remove it