General Grading Notes: American Marble Auctions grading goes by a numbering system, which coincides with the condition of a marble. When you read a description, we will talk about the condition of the marble in detail and assign a grade number to it. For instance, it might say, “this marble has some minor pocket wear and grades a 9.1”. This number reflects the things we talk about and any flaws or distractions from a marble being perfect. American Marble Auctions proudly can say that we only deal with marbles that are above 8.5 near mint grade. We would consider selling a marble below 8.5 grade if the marble is extremely rare and desirable, but will not consider selling any marble below 8.0 grade. Our group of experts will examine every marble under 10-45X magnification and in bright indoor and outdoor light.
Grade versus Value: A marble’s value depends on many factors including rarity, condition (grading), size, eye appeal etc. All these factors will add to the value of the marble. Condition of the marble, which is numbered with a grade, is one of the most important factors of the final valuation. Having said that, how is a grade affects the value? A tiny microscopic nick takes the marble from mint grade down to near mint grade. Since marbles are very small objects compared to many other glass collectibles, a microscopic damage makes a big difference. So, mint graded (9.0 to 9.5) marbles will have a higher value compared to near mint marbles (8.0 to 8.9). An important note to the bidders is that high premium grade (9.6 to 9.9) marbles will always have higher value. Our estimate values will be based on this philosophy.
8.0-8.4 Near mint minus
Heavy pocketware and damage. Overall visible nicks and/or loss of surface shine.
8.5-8.9 Near mint
Marble has damage and glass loss. Damage is not as made. Surface should still be glossy wet on higher grades. Minor pocket ware may be present.
9.0-9.4 Mint Minus
Marble has no glass loss, but may have minor as made imperfections. As made glass voids, surface creases or air pops on surface may be present. Marble should have original wet surface. Marble may be as made out of round.
Marble has original glossy wet as made surface. As made imperfections do not present any glass loss, air pops or any major creases. Marble should be round.
MARBLE SIZE MEASURING
We place great importance on measuring the marble with complete accuracy. We use digital calibers to measure down to 0.0001”. When we give a dimension it is always the widest point of the marble. If the marble is out of round, we note this in the description and mark it in grading of the marble. When measuring a marble, we place the marble in the caliber and rotate the marble until the caliber does not go up. That is the widest point of the marble.