Mibs equals handmade, art glass-marbles (or glass marbles in general, but I only include artistically fit, contemporary marbles for my definition).
As of autumn 2006, amazing artists, such as KENAN TIEMEYER, DREW FRITTS, BRAD BRANDOLINO (the Matrix Man), KEVIN O'GRADY, DAVID SALAZAR, etceteras, expand the possibilities to a frenzied degree. Of note, the fume technique is causing havoc among addicts, at the moment. Bidding war usually occur on Ebay and other sites. Uranium inclusion is always a welcome diversion. And opticals are rare among mibs, and I am not talking about vortices, either. Huge marbles, 2.60 inches in diameter or more, are a must. Personally, I stay away from drab, puny mibs, those that are less than 1.30 inches in diameter, especially with morose colors. And unintentional bubbles in the design vex most marble collectors, and these are usually a sign of carelessness in one's work, or even lacking in skills -- an amateur, perhaps?