Poudretteite — A Quebec Curiosity That Became a Burmese Collector Stone
Poudretteite — A Quebec Curiosity That Became a Burmese Collector Stone
An exceptionally rare pink borosilicate first found at Mont Saint-Hilaire, only later cut as gem rough from Mogok
Poudretteite is an exceptionally rare cyclosilicate (more precisely a ring borosilicate) of potassium and sodium with the formula KNa2B3Si12O30. It was first identified in 1965 in the Poudrette quarry on Mont Saint-Hilaire, Quebec, where it occurred as small colourless crystals in a marble xenolith embedded in nepheline syenite, and named in 1986 for the Poudrette family who operated the quarry. For three and a half decades it was a mineralogical curiosity rather than a gem species; gem-quality, faceted poudretteite did not appear in the trade until the discovery of pink Mogok material in 2000, since when it has become one of the most sought-after collector stones at the cabinet end of the market.
Mineralogy
Poudretteite is hexagonal and crystallises in the osumilite structural family. The Mont Saint-Hilaire crystals are colourless and rarely exceed a few millimetres; the Mogok stones, found in marble in the Pyaung Gaung tract north of Mogok town, occur as pink to purplish-pink crystals up to several centimetres long. Hardness is 5 to 5.5 on the Mohs scale — soft for daily-wear ring use — and specific gravity is around 2.50 to 2.53. Refractive indices are approximately 1.511 to 1.532, with a small birefringence of 0.020 to 0.021. Strong dichroism is reported in pink stones, with deeper pink in one direction and near-colourless in the other, an important orientation cue at the cutter's bench.
The pink colour in Mogok material is attributed to trace manganese; treatment to deepen colour has not been documented in the trustworthy gemmological literature for this species, in part because the supply is so small that no commercial treatment programme has emerged. Buyers should still ask for a laboratory report at the carat weights at which serious money changes hands.
The 2000 Mogok discovery
The first faceted gem-quality poudretteite was a 3-carat pink stone reported by GIA in 2000, sourced from Mogok via the Bangkok dealer market. Subsequent finds in the early 2000s yielded the largest known clean faceted stone, a 9.41-carat cushion held in the Smithsonian's National Gem Collection, along with a small handful of stones in the 2 to 5 carat range. Production has been sporadic since; new material reaches the market in single-piece quantities rather than parcels, and confirmed faceted stones over 1 carat are estimated in the low hundreds globally.
Identification
Poudretteite is most easily distinguished from pink tourmaline, morganite, kunzite, and pink topaz by refractive index, specific gravity, and dichroism, but the small published reference dataset means a competent laboratory should always be consulted on stones of consequence. Inclusion suites in Mogok material include marble-host minerals — calcite, scapolite, and humite-group phases — that are useful identifiers. GIA, SSEF, and Gübelin have published gemmological notes on faceted poudretteite specimens.
In the trade
The market for poudretteite is small, specialist, and primarily collector-driven. Stones rarely appear at trade shows; the typical pathway is private treaty between dealers and collectors of rare species. Prices for clean pink stones over 1 carat have reached five figures per carat at the upper end. The species is not realistic as a commercial jewellery stone — both because of the supply and because the hardness places it in the protected-setting tier — but it has earned its place in the rare-stone canon alongside taaffeite, jeremejevite, and benitoite.
Because supply is unpredictable and identification depends on a small reference dataset, any poudretteite at a meaningful price point should ship with a current GIA, SSEF, Gübelin, or AGL report.