The term orange peel effect is often used to refer to the uneven appearance of the polished surface of jadeite, which arises due to the hardness anisotropy of its mineral grains arranged in different directions. The unusual orange peel effect observed on white nephrite from Russia has been preliminarily recognized in the commercial sphere, but minimal description of the underlying causes for the effect exists in the literature. In this investigation, this orange peel surface feature, which includes granular pits and bumps, pseudo-rhombic microstructure, and subparallel fissures, was explored using gemological and petrographic microscopes, an electron probe microanalyzer with backscattered electron imaging, and cathodoluminescence imaging. The observed surface feature, related to pseudomorphs, results from metasomatism where nephrite (tremolite) replaces rhombic carbonate (dolomite) mineral grains while preserving their original microstructure. Petrographic observations show that the pseudo-rhombs on these pseudomorphs are intersected by a network of veins, similar to the framework of cleavage patterns of calcite or dolomite. The pseudo-rhombs ranged from 100 to 500 μm in width, consisting of a thin vein outline and an inside region composed of fine compacted fibers, with a relatively less compact central domain. This study demonstrates that this effect is largely dependent on the nephrite’s adopted microstructure rather than its chemical composition or mineral components. Derived from these results, a formation model of this distinctive microstructure is proposed, arising from fluid flow and precipitation accompanied by volume shrinkage reactions during replacement progress. Based on the review of the microstructures of available white nephrite samples from other localities, the pattern of pseudomorphs with pseudo-rhombs and claw lineation is a unique feature of Russian nephrite.

Article link: https://www.gia.edu/gems-gemology/fall-2025-white-nephrite