‘Sugar’ Nephrite from the Altun Mountains, Xinjiang, China

Nephrite has a long history and profound cultural significance in China, along with a vast consumer market. In July 2025, author YG conducted a field trip to nephrite mining areas in the Xinjiang Uygur Autonomous Region of north-western China, and personally collected different varieties of nephrite from multiple sites. Among them was a type known as ‘sugar’ nephrite (tang bai liao), which has attracted significant attention due to its distinctive visual appearance that shows alternating brown and white colouration. Since the brown sections resemble the hue of brown sugar, and the white parts look like white sugar, overall it presents a ‘sugary’ appearance, providing its colloquial name in the jade trade. This material comes from nephrite deposits in the Altun Mountains (or Altyn-Tagh region) in south-eastern Xinjiang (Fang et al. 2024), with the nearest administrative areas being Ruoqiang County and Qiemo County. This region hosts approximately 300–400 active jade-mining sites.

A representative sample of ‘sugar’ nephrite that weighed approximately 19.8 g and measured 40 × 18 × 17 cm (Figure 5) was characterised for this report. It contained two parallel brown bands—one at the top and one at the bottom—sandwiching a white section between. In the jade trade, this symmetrical structure is referred to as ‘heaven and earth sugar’ (tian di tang), symbolising ‘heaven above, earth below and humanity in between’, representing a meaningful natural formation.

Infrared spectroscopy confirmed that both colour portions of the sample were composed of tremolite, as expected for nephrite jade (Zhang et al. 2022), with no detectable presence of other minerals such as actinolite.

UV-Vis-NIR spectra of the differently coloured areas of the sample are shown in Figure 6. The brown zones exhibited a distinct broad absorption band centred at 430 nm, while the white area primarily displayed an absorption maximum at 340 nm. Both the white and brown portions exhibited an absorption band at ~950 nm, which is attributed to the presence of OH^- groups within the nephrite structure (Jutras et al. 2023).

Although Mn, Fe and Ti are well-established chromophores in yellow nephrite (Jiang 2020), the origin of brown coloration has been attributed either to the presence of Mn³⁺ and Fe³⁺ (Yu et al. 2016) or to goethite micro-particles (Han et al. 2013). The cause of the white-to-brown colour variation in ‘sugar’ nephrite remains unresolved due to a paucity of dedicated studies. To investigate the trace-element distribution in this material, a linear traverse of 40 points was analysed across the brown and white zones of the sample (see arrow in Figure 5) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The analyses were performed using a PlasmaQuant MS Elite ICP-MS (Analytik Jena, Germany), with high-purity Ar as the nebuliser and auxiliary gas, and high-purity He as the carrier gas. Laser ablation was carried out with an NWR-213 system (Elemental Scientific Lasers, USA) using an energy density of 8 J/cm², a spot size of 50 µm and a repetition rate of 10 Hz. NIST SRM 610 and 612 glass standards were used for external calibration, and data reduction was undertaken with the Iolite software package.

UV-Vis-NIR Spectra

As shown in Table II and Figure 7a–e, Mn, Fe and Ti were enriched in the brown zones and depleted in the white area. By contrast, Cs and W were enriched in the white core and depleted in the brown zones. These trends were confirmed using a Pearson correlation coefficient (a statistical measure of linear correlation between two variables, symbolised by r, with 1.0 equalling a perfect correlation): Mn correlated strongly with Fe (r = 0.98; Figure 7f) and Ti (r = 0.90), whereas its relationships with Cs (r = –0.63) and W (r = –0.56) were markedly negative. Collectively, these data show that the transition metals Mn, Fe and Ti preferentially occur in the brown zones, while the large-ion-lithophile element Cs and high-field-strength element W concentrate in the white area.

Table II: Chemical composition by LA-ICP-MS of selected elements along the 40-point linear traverse across the nephrite sample (in ppm).

Trace-element Composition

Figure 7: Chemical analyses of the nephrite sample by LA-ICP-MS along the linear traverse shown in Figure 5 indicate that Mn, Fe and Ti are concentrated in the outer brown zones (a–c), while W and Cs are enriched in the central white zone (d, e). A graph of Mn vs Fe (f) shows the strong correlation between these two elements.

The presence of enriched amounts of Mn, Fe and Ti in the brown zones as compared to the white area strongly suggest that these elements are involved with producing the brown colouration. Further investigations into the specific colour-forming mechanisms of the brown and white domains of this nephrite are needed to advance our understanding of this material and its formation.

Yujie Gao, Tiantian Huang(candice.huang@guildgemlab.com)and Qi LuGuild Gem LaboratoriesShenzhen, China

References

Fang, T., Chang, Y. & Yang, M. 2024. Nephrite from Xinjiang Qiemo Margou deposit: Gemological and geochemical insights. Minerals, 14(5), article 458, https://doi.org/10.3390/min14050458.

Han, W., Hong, H., Wu, Y. & Yin, K. 2013. A study on the colouring mechanism of “sugar” Hetian jade. Spectroscopy and Spectral Analysis, 28(5), 1005–1009 (in Chinese with English abstract).

Jiang, Y. 2020. Research on the mineralogical petrological characteristics and genesis mechanism of Hetian jade in Ruoqiang, Xinjiang. PhD dissertation, China University of Geosciences, Beijing, China (see pp. 81–85; in Chinese).

Jutras, J.-P., Rossman, G.R., Williams, B. & Williams, C. 2023. Nephrite jade from Washington State, USA, including a new variety showing optical phenomena. Journal of Gemmology, 38(5), 494–511, https://doi.org/10.15506/jog.2023.38.5.494.

Yu, H., Wang, R., Guo, J., Li, J. & Yang, X. 2016. Color-inducing elements and mechanisms in nephrites from Golmud, Qinghai, NW China: Insights from spectroscopic and compositional analyses. Journal of Mineralogical and Petrological Sciences, 111, 313–325, https://doi.org/10.2465/jmps.151103 (in Chinese with English abstract).

Zhang, X., Shi, G., Zhang, X. & Gao, K. 2022. Formation of the nephrite deposit with five mineral assemblage zones in the central western Kunlun Mountains, China. Journal of Petrology, 63(11), article egac117, https://doi.org/10.1093/petrology/egac117.