What term describes rough that has been ground to the approximate shape of the finished stone?

The term "preform" refers to rough material that has been shaped or ground to an approximate form of the final cut gemstone. This process typically involves removing excess material to create a more manageable piece for further refining. Preforms are essential in gemstone cutting, as they set the stage for achieving the desired final shape and facets of the finished stone.

This method allows lapidaries to visualize the final stone's proportions and evaluate any inclusions or features that may affect the finished product. Preforming is a critical step in the overall gemstone finishing process, ensuring the cut is efficient and aligns with the gem's intended design. The other terms do not accurately describe this intermediate stage in gemstone preparation, as they refer to different aspects of the cutting and shaping processes.