The most popular method of prospecting for loose Herkimer Diamonds is by breaking them out of a single rock. Domed pocket mining in the table - layer of the rock is usually very rich with diamonds. Some pockets are known to contain thousands of diamonds. Pockets or cups can be up to six feet in diameter and usually no less than one foot. Occasionally, the top will be beautiful black drusy quartz.
Pockets containing diamond crystals are never the same either in size or in quality.
Most pockets, as a rule, will contain diamond crystals of various sizes. Some pockets may contain large crystals ranging in size from four to eight inches long and three to four inches wide. Other pockets with medium sized crystals range in size from an inch and a half to three to four inches long and a half inch to two inches wide. Micro crystals are always found. As the crystals move up in size they tend to become less clear or more translucent than transparent.