Plum Garnet — Reddish-Purple Trade Designation
Plum Garnet — Reddish-Purple Trade Designation
A descriptive term for rhodolite and pyrope-almandine intermediates
Plum garnet is a trade descriptor for garnets exhibiting a reddish-purple to purplish-red hue reminiscent of plum skin, applied principally to rhodolite garnet and to pyrope-almandine intermediates whose colour falls in the appropriate range. The name is descriptive rather than scientifically defined: there is no mineralogical species called plum garnet, and the term is used in retail and dealer contexts as a colour descriptor that consumers find evocative. Plum garnets are valued for the saturation and depth of their colour and for their relative rarity in the broader garnet market.
Composition and species
Most stones marketed as plum garnet are rhodolite — a pyrope-almandine intermediate with the approximate formula (Mg,Fe)3Al2(SiO4)3 and a composition typically biased toward the pyrope end of the series. Rhodolite was named in 1898 by George F. Kunz from the Greek rhodon (rose) for material from North Carolina; the species has since been documented in commercial quantities from Mozambique, Tanzania, Madagascar, India, Sri Lanka, and Brazil. The reddish-purple character that defines rhodolite is the same chemistry that produces plum garnet at deeper saturations.
Some plum garnet material is closer to almandine in composition, with a slightly browner or more saturated red, and some falls into the umbalite or grape-garnet trade categories that overlap with plum at the boundaries. The trade colour descriptions are not strictly delimited and dealer practice varies.
Trade position
Rhodolite garnet has been commercially significant since Mozambican production scaled in the 1980s and 1990s, and the saturation range that the term plum garnet describes is at the upper end of the rhodolite quality spectrum. Material is bought principally by Indian and Thai dealers, cut in Jaipur and Bangkok, and supplied to the international market as faceted goods. Pricing is well below corundum or fine spinel of comparable colour but above the wider commercial garnet market.
For the buyer, plum garnet is a clear descriptor for the colour wanted but not a guarantee of any particular species or origin. A laboratory report will identify the stone as rhodolite or pyrope-almandine, with composition and origin opinion where determinable.
In the trade
Plum garnet is sold without the disclosure complications that affect ruby, sapphire, or emerald, because routine garnet treatment is not a market issue. The category is straightforward: the colour is what the buyer is paying for, the species is rhodolite or close to it, and the value is set by colour saturation, clarity, and cutting quality. Plum garnet is a working trade term, not a regulated category.