Below is the descriptive and numeric grading system adopted by Marble Collectors Society of America ( P.O. Box 222, Trumbull CT 06611). It is the system of grading adopted by most marble dealers and the grading used on our website.
Mint: A marble that is in original condition. The surface is unmarked and undamaged. There may be some minor rubbing on the surface, however, the marble is/ just the way it came from the factory. (10.0-9.0)
Near Mint: A marble that has seen minor usage. There may be evidence of some hit marks, usually tiny subsurface moons, pinprick chips, tiny flakes or tiny bruises. The damage is inconsequential and does not detract from viewing the marble. (8.9-8.0)
Good: A marble that has seen usage. It will have numerous hit marks, subsurface moons, chips, flakes or bruises. The core can still be seen clearly, but the marble has obviously been used. (7.9-7.0).
Collectible: A marble that has seen significant usage. Overall moons, chips, flakes and bruises. The core is completely obscured in some spots. A Collectible marble has served its purpose and been well used. (6.9-0.0).
Other marble collector terms in common usage and used here
Fleabite: A pit-like hit mark mostly visible under 10x magnification.
Tick: A pit-like hit just comfortably visible to the naked eye.
Chip: Loss of glass from impacts easily noticeable with casual observation.
Sparkle: a tiny internal reflection resulting from a bang to the marble.
Moon: An internal reflection visible with the naked eye as a circular or ringlike area resulting from a hard hit to the marble.
Stress Fracture: An as-made fracture in the marble that typically results from uneven cooling of different types of glass in the marble.