The trade definition

Imperial jade refers to the top colour grade of jadeite jade, characterised by an even, saturated emerald-green colour, high translucency, and the absence of distracting colour zoning, fractures or inclusions visible to the unaided eye. The grade is recognised informally across the trade and used in major auction nomenclature at Christie's and Sotheby's Hong Kong, although it is not formally codified by any single laboratory or industry body. The Chinese term fei cui, properly applied to all jadeite, is sometimes restricted in domestic Chinese trade to imperial-grade material, with lower grades labelled by colour and by translucency separately.

Mineralogy and source

Jadeite is a sodium aluminium silicate of the pyroxene group, distinct from nephrite, which is a calcium magnesium silicate of the amphibole group. The two materials are mineralogically unrelated and were not distinguished in the trade until the late nineteenth century, when chemical analysis established that what had been sold under the single name jade was in fact two different stones.

The principal source of jadeite, including all imperial-grade material, is the Mogaung mining region of Kachin State in northern Myanmar, formerly Burma. Secondary sources in Guatemala, Russia and Japan produce jadeite, but commercial production at imperial colour grade is overwhelmingly Burmese. The Burmese deposit was first commercially exploited in the eighteenth century by Yunnanese Chinese traders, and the supply chain into China has continued, with interruptions, ever since.

The colour mechanism

The emerald-green colour of imperial jade is caused by chromium replacing aluminium in the jadeite crystal structure. The interaction between chromium content and the optical scattering caused by the polycrystalline aggregate texture of the stone produces the characteristic combination of saturated green colour and high translucency. Iron content, ubiquitous in jadeite, can dull the colour toward yellow-green or grey-green when present at higher levels. Top imperial material has chromium high enough to produce the colour and iron low enough to keep the colour clean.

The price escalation

The price escalation between commercial-grade jadeite and imperial-grade jadeite is among the steepest in the gemstone trade. A bangle of even, translucent commercial green might sell at five thousand US dollars; the same form in imperial colour and translucency might sell at five million. The Hutton-Mdivani jadeite bead necklace, sold at Sotheby's Hong Kong in 2014 for twenty seven and four tenths million US dollars, remains a benchmark, but several imperial bead necklaces have crossed similar levels in the decade since.

The premium reflects two factors: the rarity of large stones at imperial grade, and the depth of the Asian market for the material. Chinese, Hong Kong and Singaporean buyers dominate the high end of the jadeite market, and the price discovery happens predominantly at the Hong Kong spring and autumn auction series.

The treatment problem

The market is haunted by the treatment problem. Polymer-impregnated jadeite, known in the trade as B jade, is impregnated with epoxy resin to fill internal fractures and improve apparent transparency. The treatment can dramatically improve the appearance of low-grade material, raising the apparent grade by two or three steps, but it is unstable in the long term. Polymer-impregnated jadeite yellows over decades and the treatment is detectable by infrared spectroscopy.

The trade convention, codified by the GIA, the LMHC and major Asian laboratories including the Hong Kong Jade and Stone Laboratory and the GIT in Bangkok, recognises three categories: Type A, untreated; Type B, polymer-impregnated; and Type C, dyed. Imperial-grade jadeite is by definition Type A, and laboratory certification of Type A status is essential for any high-value piece.

Dyed jadeite, Type C, is treated with green dye to imitate imperial colour. The dye is detectable by spectroscopy and by careful examination under magnification, where the dye accumulates in fractures and grain boundaries. Type B and C combination treatment, polymer-impregnated and dyed, is also produced and is similarly detectable.

Cutting forms

The principal cutting forms for imperial jade are the cabochon, the bead, the bangle, and the carved figure. Faceted jadeite is rare and trades at a discount per carat compared to comparable cabochon material, since the polycrystalline aggregate texture does not benefit from facet light return the way single-crystal material does. The cabochon and bead forms maximise the visual interaction between the colour and the translucency, which is what the market values.

Bangles command particular premiums because they require unusually large blocks of consistent colour to produce. A single bangle requires a continuous loop of imperial-grade material approximately seven to eight centimetres in inner diameter and twelve to fifteen millimetres in cross-section, all without significant colour zoning, fracture or inclusion. The yield from any given block of rough is low, and most blocks of imperial-grade rough cannot produce a single bangle.

Authentication and the buyer's discipline

For the working trade, the operative checks on a stone offered as imperial jade are: laboratory confirmation of jadeite identification (versus nephrite, serpentine, hydrogrossular or chalcedony imitations), Type A confirmation by infrared spectroscopy, and an evaluation of colour and translucency against current market reference standards. Auction houses publish their own reference grading scales, and the Hong Kong-based Gemological Institute of Hong Kong publishes the most widely cited reference for the trade.

The price ceiling for imperial jade is established by the auction record, which now sits in the high tens of millions of US dollars for premier necklace lots. Private treaty sales in Hong Kong, Beijing and Singapore are reported to cross these levels for unsold or never-marketed material, although such sales are not publicly documented.