Agate marbles, or “aggies” (if you want to use mibster lingo) are a kind of marble made of agate, a colored variety of quartz. Agate marbles were the preferred shooter for many marble players because they are denser than glass or clay marbles. Popular from the 1860s until World War I, most agates were hand cut and produced in Germany. After the war, new technology allowed for glass marbles to be mass produced. During the heyday of marble playing, several American glass marble manufacturers like Akro Agate Co. and Christensen Agate Co. had the word “agate” in their name to suggest their marbles were similar to actual agates.
While other minerals were used to make marbles, like malachite (the green one on the left) and turquoise (the blue one on the right) spheres above, they probably weren’t intended for playing ringer or any shooting marble game (you wouldn’t want to lose them in a game of keepsies after all!). Instead, marbles made with semi-precious stones were intended for a variety of tabletop board games like solitaire.