(MM)  Micro mineral - a small (typically less than 1") piece of matrix with micro crystals unmounted. The term "micro mineral" depends more on the size of the crystals or specific mineral than it does on the size of the matrix. Requires magnification to identify or evaluate.

(MT) Micro mount - a mounted micro specimen, usually in a standard "micro mount" size box (Dimensions: 1.0" x 1.0" x 0.75" (2.54 cm x 2.54 cm x 1.90 cm). The matrix, where present, is typically 3/8 inch or less in maximum dimension. Some micro mounts may consist of a single crystal mounted with no matrix.

(TN) Thumbnail - fits in a standard “Perky" box dimensions 1.25" x 1.25" x 1.25" (3 cm cube).

(SC) Small cabinet - 1.25 to 4 inches (3 to 10 cm) across maximum dimensions.

(LC) Large Cabinet – 4 to 6 inches (10 to 15 cm) across maximum dimension.

(MUSEUM) Museum (or Extra Large Cabinet)- more than 6 inches (15 cm) across maximum dimension. These extra large specimens are commonly referred to as museum…not to designate quality, but only to designate size. XL or XLS cannot be used as XL / XLS are the mining abbreviations for crystal / crystals

These size classifications are not universal. Different mineral dealers may have slightly different dimension standards for what they consider to be miniature, small cabinet, large cabinet and museum or extra-large cabinet. The dimensions for Thumbnail and Micro mount sized minerals are fairly standard because the standard display boxes limit their size.