Over the past ten years, gemological laboratories have been replacing film-based microradiography with real-time X-ray microradiography (RTX). This paper compares the output quality and resolution provided by two RTX units fitted with different detectors: an image intensifier (II) and a flat panel detector (FPD) using the same type of Xray generating tube. Although the II is faster and less expensive, the images acquired with the FPD show greater detail of the pearl’s internal growth structures, making interpretation and consequent conclusions easier to validate.