Eggplant: The Aubergine Body Colour of Tahitian Cultured Pearls

One of the rarest and most prized colour categories within the Tahitian pearl spectrum

Eggplant — also rendered in trade usage as aubergine — is a recognised body-colour classification applied to Tahitian cultured pearls displaying a deep purple-brown to blue-violet hue reminiscent of the skin of a ripe aubergine fruit. It sits at the darker, more saturated end of the Tahitian colour spectrum, distinct from the commoner silver, grey, and charcoal categories, and is widely regarded by pearl traders, grading laboratories, and auction specialists as one of the most desirable and commercially valuable colour expressions that the black-lipped oyster Pinctada margaritifera can produce.

Biological Origin of the Colour

The body colour of any Tahitian cultured pearl is determined by the nacre deposited by the mantle tissue of the host mollusc, Pinctada margaritifera var. cumingi, the black-lipped pearl oyster native to the lagoons and atolls of French Polynesia. Nacre is composed of aragonite platelets bound by an organic biopolymer matrix of conchiolin proteins and polysaccharides. The specific colouration arises from two interacting mechanisms: selective light absorption by organic pigments — principally porphyrins and their derivatives — embedded within the conchiolin layers, and thin-film optical interference produced by the regular stacking of aragonite platelets.

In eggplant pearls, the porphyrin pigment concentration and distribution shift the dominant absorbed wavelengths toward the red-orange range, leaving a residual body colour in the violet-to-purple-brown register. The precise chemistry is influenced by the genetics of the donor mantle tissue used to seed the pearl, the health and diet of the host oyster, water temperature, and the mineral composition of the lagoon environment. Because these variables must align in a particular way to produce a true eggplant body colour, the category is statistically less common than grey or silver within any given harvest, which underpins its market premium.

Colour Description and Grading

Gemmologically, eggplant body colour occupies a narrow band within the Munsell or CIE colour space: hue ranging from a reddish-purple through blue-purple, with medium-to-dark tone and moderate-to-strong saturation. The GIA pearl grading system, as documented in Gems & Gemology and GIA's pearl grading course materials, describes Tahitian pearl body colours along a continuum from white and silver through grey, green, blue, purple, and brown, with eggplant representing the deeper purple-brown intersection of that continuum.

In practical trade grading, evaluators assess body colour under standardised daylight-equivalent illumination (approximately 5,500–6,500 K), viewing the pearl against a neutral grey background. An eggplant designation requires that the dominant hue be unmistakably purple-brown rather than a cooler blue-grey or a warmer chocolate-brown. Borderline specimens are sometimes described as dark purple or plum, though eggplant and aubergine are the terms most consistently used in auction catalogues and wholesale price lists.

Overtones and Orient

Body colour is only one dimension of a Tahitian pearl's visual character. Equally important are overtone — the translucent secondary colour floating above the body colour — and orient, the iridescent play of spectral colours arising from diffraction at the nacre surface. Eggplant pearls most frequently display overtones described in the trade as peacock (a green-to-teal secondary colour) or cherry (a pinkish-red secondary colour). The combination of a deep aubergine body with a strong peacock overtone is particularly prized, as the contrast between the warm purple-brown ground and the cool iridescent green creates a visual complexity that is difficult to replicate in any other gem material.

Orient, when present in eggplant pearls, tends to appear as a shifting rainbow sheen concentrated near the pearl's equator or at its drill-hole edges. High orient is associated with finely structured nacre — thin, regularly stacked aragonite platelets — and is considered a mark of superior quality regardless of body colour category.

Principal Origins

Eggplant-coloured Tahitian pearls are produced almost exclusively within the exclusive economic zone of French Polynesia, the archipelagos of which — the Tuamotu-Gambier group, the Gambier Islands, and the Society Islands — constitute the world's primary source of Pinctada margaritifera cultured pearls. The Gambier Islands, and particularly the atoll of Mangareva, have a long-standing reputation among pearl farmers and traders for producing pearls with deeper, more saturated body colours, including eggplant and dark cherry, attributed in part to the cooler, nutrient-rich waters of that southern group.

Smaller quantities of eggplant-coloured pearls have been reported from Pinctada margaritifera farms in the Cook Islands and, occasionally, from operations in the Marshall Islands and Micronesia, though French Polynesia remains the dominant and most commercially significant source. The French Polynesian government's pearl quality regulations — administered through the Groupement Interprofessionnel pour la Promotion de la Perle de Tahiti (GIE Perles de Tahiti) — prohibit the export of pearls with nacre thickness below 0.8 mm, a standard that helps ensure the colour depth and lustre associated with premium eggplant specimens.

Size, Shape, and Nacre Quality

Eggplant body colour is encountered across the full range of Tahitian pearl shapes — round, near-round, oval, drop, button, circle, and baroque — though round and near-round specimens in this colour category attract the highest per-pearl premiums. Commercially significant sizes for eggplant Tahitians typically range from 9 mm to 14 mm in diameter, with larger examples above 14 mm being considerably rarer and commanding exponentially higher prices.

Nacre quality is paramount in evaluating eggplant pearls. Thick, evenly deposited nacre — ideally 1.5 mm or more — produces the depth of colour and the mirror-like lustre that distinguishes a fine eggplant pearl from a merely acceptable one. Thin nacre, even when the body colour is correct, results in a chalky or washed-out appearance and may allow the nucleus to show through as a faint ring under raking light, a defect known in the trade as blinking.

Treatment and Simulants

Tahitian pearls, including those sold as eggplant, are generally not subjected to the bleaching and dyeing treatments routinely applied to freshwater and Akoya cultured pearls. However, the trade is not entirely free of colour enhancement. Some pearls are irradiated — typically by gamma irradiation — to deepen or shift body colour, a process that can produce dark blue-grey or purple-brown hues superficially resembling natural eggplant colouration. Irradiation-induced colour in pearls tends to be concentrated in the outer nacre layers and may be detected by gemological laboratories through spectroscopic analysis and, in some cases, by the characteristic metallic lustre it imparts.

Dyeing with organic colorants is also practised on lower-grade material. Dyed pearls can be identified under magnification by the concentration of colourant in surface features such as drill holes, growth rings, and surface irregularities. Reputable laboratories — including GIA's pearl identification service and the SSEF Swiss Gemmological Institute — offer testing specifically for natural versus treated colour in Tahitian pearls, and certificates from such laboratories are increasingly expected for high-value eggplant specimens in the auction market.

Glass, shell, and plastic simulants in eggplant hues exist in the costume jewellery market but are readily distinguished from genuine nacre by their lack of orient, their uniform surface appearance, and their behaviour under ultraviolet fluorescence.

Market Context and Value Factors

Within the Tahitian pearl market, eggplant body colour consistently commands a premium over the more abundant silver and grey categories at comparable size, shape, nacre quality, and lustre grades. Auction results from major houses — including Christie's, Sotheby's, and Bonhams — document strong demand for eggplant and aubergine Tahitian pearl necklaces and earring suites, particularly when the pearls are well-matched in colour and overtone. The challenge of assembling a matched strand of eggplant Tahitians — requiring the selection of pearls from multiple harvests and farms — contributes substantially to the value of finished jewellery in this colour.

Wholesale pricing for eggplant Tahitians is influenced by the same hierarchy of value factors that governs all cultured pearls: lustre (the single most important factor), surface cleanliness, nacre thickness, shape, size, and colour. A fine round eggplant pearl of 12 mm with high lustre, clean surface, and a strong peacock overtone may trade at a multiple of three to five times the price of a comparable grey pearl from the same harvest. Retail premiums are correspondingly significant.