Diopside, an important component of the crustal and upper mantle, plays an important role in the formation of nephrite. Polysynthetic twinning in natural diopside, especially from skarns, has rarely been systematically researched. Here, the polysynthetic twinning of natural diopside was investigated in two skarn-type nephrite deposits (Niewang and Tatliksu) in Qiemo, Xinjiang, China. Petrographic observations revealed periodic alternations of dark–light lamellae under cross-polarized light and parallel striations under plane-polarized light, whereas backscattered electron images indicated high homogeneity, which suggested a type of mechanical polysynthetic twinning. According to the optical indicatrix, twins were predominantly oriented as a (100)[100] system. Raman spectra and chemical data show that pyroxenes in nephrite are close to the Di end-member with 0.90–1.04 a.p.f.u. Mg and 0.98–1.05 a.p.f.u. Ca. Both diopside and tremolite from Tatliksu contain slightly higher Fe than those from Niewang. Given the seismic origin of mechanical clinopyroxenes twins, twins of studied diopsides are likely to be attributed to Paleozoic-Mesozoic paleoearthquakes in the Altyn Mountain. A shear stress ≥ 140 MPa and a differential stress greater than 280 MPa are suggested as conditions linked to generation of the twinning of diopsides in the nephrite deposits. The replacement of diopside by tremolite along its twin planes highlights the potential gemological implications, as such replacement by tremolite probably facilitated the formation of dense, fine fibre textures in the nephrites.

Recently, a variety of nephrite containing localized pink mineral aggregates has emerged on the market, which is sometimes referred to as “peach blossom jade” by some merchants. Currently, there is limited research on this type of nephrite containing pink minerals, and its detailed mineral composition characteristics and coloration mechanisms remain unclear. In this study, four samples of nephrite containing pink minerals were systematically investigated using conventional gemological tests, as well as modern analytical techniques such as X-ray powder diffraction (XRD), infrared spectroscopy (IR), laser Raman spectroscopy, ultraviolet–visible (UV-Vis) absorption spectroscopy, electron probe microanalysis (EPMA), and X-ray fluorescence spectroscopy (XRF). These techniques were employed to elucidate the mineral composition, chemical composition, spectroscopic features, and coloration origins of the samples. The results indicate that the primary mineral constituent of the samples is tremolite, with accessory minerals including zoisite, muscovite, orthoclase, andesine, diopside, and prehnite. The major chemical components of the samples are SiO₂, CaO, and MgO, along with minor amounts of Al₂O₃, K₂O, and FeO_T. The overall green hue of the samples is positively correlated with Fe content. The pink mineral present in the samples is predominantly Mn-bearing zoisite, and the pink coloration of zoisite is primarily attributed to the energy level transitions of Mn²⁺ at approximately 540 nm and 440 nm.

Featuring subtle lithological alterations in the host rocks and containing colossal gemstone crystals, the scheelite deposit at Xuebaoding in the Pingwu region of Sichuan Province exhibits characteristics typical of a vein-like hydrothermal-type deposit. The scheelite from the Xuebaoding region is renowned for its high saturation of color, perfect crystal shape, and pure color. In this study, its crystal structure and mineralogical, geochemical, and in situ Sr-Nd isotope characteristics are all systematically characterized. Our objective is to determine the source of ore-forming materials, the timing of the mineralization, and the chemical composition of scheelite, including major elements, trace elements, and rare earths elements (REE). The scheelite samples were analyzed with a variety of methods such as polarizing microscopy, X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), electron probing, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In addition, conventional gemological tests were performed using instruments including gemstone microscopes, GI-UVB ultraviolet fluorescent lamps, grating spectroscopy, etc. The results demonstrate that scheelite exhibits a high refractive index, excellent crystallinity, and a granular structure. Clear color bands and ring structures are observed within the minerals, accompanied by interference colors of light blue, blue, and yellow. Additionally, the mineral components are relatively concentrated, with muscovite and illite serving as accessory minerals. Furthermore, the chemical composition of scheelite reveals a WO₃/CaO mass ratio that approaches or exceeds the ideal value. Moreover, it exhibits a wide range of variations in total rare earth element (∑REE) content, which is characterized by an enrichment of light rare earths (LREE), significant negative Eu anomalies, and insignificant Ce anomalies. In addition, the metallogenic formation of scheelite can be estimated to have occurred during the Toarcian stage in the Lower Jurassic Epoch period, approximately 183 Ma. The study further revealed that A-type granite serves as the genesis type of scheelite, with most of the ore-forming materials originating from the upper crust and a few derived from younger crustal sources.

The Qitai silicified wood from Xinjiang, NW China, provides an exceptional archive for investigating the mechanisms of wood silicification. This study applies microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to characterize the microstructural and mineralogical features of these fossils. The results show that the samples are primarily composed of microcrystalline–macrocrystalline α-quartz having anhedral–euhedral shapes, with minor occurrences of moganite. A well-preserved structure exhibits distinct anatomic details of cellular networks, such as growth rings and rays. Magnified observation revealed that the microcrystalline quartz within cell walls grew outward from the innermost layer of the wall, suggesting silica infiltration from lumina to walls. The opposite growth of elongated columnar quartz within adjacent cell walls terminated at the position of the middle lamellae. Cell lumen infilling exhibits greater variability on filling degree and phase type. The permeation silicification of cell walls and the oligoblastic to polyblastic structure inside cell frameworks contribute to high fidelity preservation. This interpretation helps us understand how the wood structure was perfectly preserved during the silicification, thus emphasizing its significance for wood identification through its preserved structure.

The green Manas nephrite from Xinjiang (China), predominantly composed of felted tremolite fibers and typically occurring at contacts between serpentinized ultramafic rocks and enclosing basaltic–andesitic volcanics, contains diverse veins (including folded, Stage 1 straight, and Stage 2 straight varieties exhibiting ptygmatic, reticulate, and master-branching patterns, respectively) and spheroids (Type 1 and Type 2). Its provenance identification criteria have not yet been well established. This study presents geological, petrographic, and mineral chemical data from these veins and spheroids to constrain their mineral composition and texture. EPMA data indicate that the veins and spheroids are mainly composed of tremolite–actinolite fibers. The fibers in the Stage 2 branching veins are (sub-)parallel to the vein walls, whereas those in the other veins are (sub-)perpendicular to the walls. Type 1 spheroids are composed of felted fibers and commonly occur as breccia lenses within a nephrite matrix. In contrast, Type 2 spheroids are characterized by parallel-arranged fibers. The distinctive occurrence of the white (or gray) folded veins and spheroids serves as an important diagnostic criterion for provenance and is crucial for distinguishing the Manas nephrite from that of other localities.