Khotan jade is nephrite from the Khotan, also rendered Hotan, region of Xinjiang Uyghur Autonomous Region in north-western China. It is the most prestigious of the Chinese nephrite sources and the material that defined the imperial Chinese jade tradition from the Han dynasty through the Qing. The term as used in the trade refers principally to nephrite from the Yurungkash and Karakash river beds and from the Kunlun mountain deposits that supplied them.

Mineralogy

Nephrite is a tremolite-actinolite-series amphibole, a calcium-magnesium-iron silicate, distinct from jadeite, which is a sodium-aluminium silicate of the pyroxene group. Both are gem materials and both are commonly described as jade in everyday speech, but their mineralogy and behaviour are different. Khotan nephrite is generally near the tremolite end of the series, with low iron content giving the white to pale colours that the trade values most highly. The microstructure is a felted intergrowth of fine fibres, which produces the characteristic toughness of nephrite and its capacity for thin-section translucence.

Varieties

The trade recognises several varieties of Khotan jade. Yang zhi yu, mutton fat jade, is a translucent white nephrite with a slightly oily lustre, regarded as the highest grade. Bai yu is white jade more generally, including stones that lack the mutton-fat character but retain pure white body colour. Qing bai yu, blue-white jade, has a slight greenish or bluish cast. Huang yu is yellow jade, often with skin colour from natural oxidation of the river cobble. Sugar jade has brown or russet patches in white nephrite. Black jade, or mo yu, is a dark variety. Green jade and dark green jade also occur.

River-pebble character

The most highly prized Khotan jade comes as water-tumbled river pebbles from the Yurungkash and Karakash river beds. The tumbling process produces rounded forms with a natural skin of oxidised colour where the pebble has lain in the river. Skilled carvers incorporate this skin into the design, using it for accent or for figurative elements while exposing the underlying body in the main composition. River-pebble jade with retained natural skin is documented as the most valuable form in Qing-era court inventories, and contemporary Chinese collectors maintain the same hierarchy.

Quality criteria

Grading Khotan jade depends on colour purity, the fineness and uniformity of the underlying microstructure, translucence under transmitted light, the so-called oily lustre on the polished surface, and the absence of cracks, mottles, or impurities. The very best material has a body that the trade calls neng tu, which translates roughly as soaked or saturated, in which the entire stone seems lit from within. Stones above several hundred grams of this grade are extremely scarce.

Treatment and disclosure

Khotan nephrite is generally untreated. Some stones may be lightly waxed for surface protection, which is considered acceptable by the trade and laboratories. Dyeing, polymer impregnation, or heat treatment is not standard for high-grade Khotan jade and would significantly reduce value. Buyers should request laboratory certification, particularly for stones represented as natural and untreated, since the price differential between treated and untreated material is substantial.

Distinguishing from other nephrites

Other significant nephrite sources include the Sayan-Baikal region of Siberia, particularly the Vitim deposits; British Columbia and Alaska; New Zealand, where it is called pounamu; Wyoming; and Taiwan. Trace-element fingerprinting in laboratories such as those issuing reports under the GIA and Gübelin frameworks can in principle distinguish Khotan from other nephrites, although routine origin determination for nephrite is less developed than for ruby or sapphire. Visual indicators that experienced specialists use include the specific texture of Khotan river pebbles, the character of the skin, and the saturated quality of the white body.

Modern supply

The traditional river-pebble supply is significantly depleted. Contemporary Khotan production combines limited river prospecting with mountain mining of primary deposits, regulated by Chinese authorities. High-grade Khotan mutton-fat jade has reached prices that rival or exceed those of fine Burmese jadeite on a weight basis, reflecting the scarcity of remaining material rather than any new aesthetic preference.

Significance

For the trade Khotan jade is the canonical Chinese nephrite, the material against which all other nephrites are judged. Its position in Chinese culture is older and deeper than that of any other gem material, and it remains an active focus of contemporary Chinese collecting. Working jewellers and dealers handling Chinese material should expect that any pre-Qing nephrite of consequence is likely Khotan, and should price and document accordingly.