The nephrite belt in Altun Mountain-Western Kunlun Mountain region spanning approximately 1300 km in Xinjiang, NW China, constituting the world's largest preeminent nephrite deposit. The Qiemo region in the Altun Mountain is a crucial nephrite-producing area in China with demonstrating substantial prospects for future explorationl. While extant research has extensively study on secondary deposits in the Karakash River and native black nephrite deposits in Guangxi Dahua, a lacuna exists in the comprehensive investigation of black nephrite from original deposits in Xinjiang. Margou nephrite represents a recent discovery of black-toned nephrite deposits in Qiemo County, Xinjiang, warranting a comprehensive investigation into this primary source of black nephrite within the region. This scholarly inquiry deploys a suite of sophisticated analytical techniques, encompassing Polarizing microscope, electric microprobe, Backscattered Electron Image, X-ray Fluorescence, Inductively Coupled Plasma Mass Spectrometry. The rigorous experimental test is dedicated to elucidating the chemical and mineralogical composition, and further clarify the type of its genetic types of black-black cyan nephrite from Margou deposit in Qiemo, Xinjiang. Results delineate the mainly composed of tremolite-actinolite, characterized by Mg/(Mg + Fe2+) ratios ranging from 0.86 to 1.0. Minor minerals include diopside, epidote, pargasite, apatite, zircon, pyrite and iron hydroxide. Bulk-rock rare earth element patterns exhibit distinctive features such as negative Eu anomalies (δEu=0.00~0.17), decreasing light rare earth elements, a relatively flat distribution of heavy rare earth elements, and low with total REE concentrations (1.64~38.9 μg/g), concurrently, the Cr (6~21 μg/g) and Ni (2.5~4.5 μg/g) contents are conspicuously low. The magmatic influence of granite emerges as pivotal factor in the genesis of magnesia skarn hosting the Margou nephrite. The distinctive black-black cyan colour is attributed to heightened iron content, mainly associated with FeO (0.08~6.29%). The discerned chemical composition characteristics posit the Margou nephrite as an exemplar of the magnesia skarn-type nephrite deposit.

We have studied quality characteristics, chemical, mineral and isotope composition of nephrite, diopsidite and rodingite of the Nyrdvomenshor deposit in the Polar Urals. We applied the visual petrographic and mineralogical studies, X-ray spectral fluorescence, ICP-MS analysis, scanning electron microscope with the dispersive microanalysis system, oxygen isotope composition was measured. According to its quality characteristics, the nephrite is substandard. Here, uvarovite, which forms idiomorphic grains, sometimes sheath-like, less often xenomorphic elongated, and substituting chromite are commonly encountered. The nephrite was formed due to both metamorphic and metasomatic processes. Serpentinite was replaced by diopsidite, which was then replaced by nephrite. Metamorphism intensified metasomatism of the serpentinite melange and provided a cryptocrystalline tangled-fibrous structure of the nephrite. Then metamorphism and metasomatism led to the formation of omphacite and cracking of the nephrite, which reduced its quality. As these processes progressed, contribution of crustal fluid increased.