Briefly outlined below are the conventions that are used by Dan Z Rockshop when discussing size. Please note that these are merely used as a guide, if you would like exact dimensions of a specimen always feel free to ask.
Micomount - Microscope required to appreciate
Thumbnail - Less than 2.5 cm.
Miniature - Greater than 2.5 cm and less than 5.0 cm.
Small Cabinet - Greater than 5.0 cm and less than 10.0 cm.
Cabinet - Greater than 10.0 cm and less than 15.0 cm.
Large Cabinet - Greater than 15.0 cm.
There are a confusing number of different terminologies and standards used when discussing mineral dimensions. Different federations and dealers use their own personalized definitions. There is no true standard. This is further complicated by the personal preference of some dealers or collectors to use the imperial rather than the metric system. I have tried to simplify my system to make it easy to grasp in both cm and inches.