Some marbles can be valuable. I do not know much about the values and types. I only know that I really like finding them, and display all of my glass marbles in mason jars. The older clay marbles go into a display case.
Go to the Artifacts Forum and scroll down to the last item: MARBLES.
Post a picture of your marbles, and whatever questions you have. Our Tnet marble expert,, Cheese,, should be able to I.D. your marbles. I found an old bag of marbles in my attic and Cheese I.D.ed them for me.