Maw-Sit-Sit — The Burmese Chrome-Green Rock That Reads Like Jade
Maw-Sit-Sit — The Burmese Chrome-Green Rock That Reads Like Jade
A kosmochlor-jadeite-albite assemblage from the Myanmar jade belt, named for the village where it was first identified
Maw-sit-sit is an opaque-to-translucent green rock composed primarily of kosmochlor — a sodium-chromium pyroxene — with variable amounts of jadeite, albite, chromite, and other accessory minerals. It is found near the village of Maw Sit Sit in northern Myanmar, in the same broad jade belt that supplies the world's jadeite, and was first formally identified and named by Eduard Gübelin in the 1960s. Though commonly grouped with jade in the trade, maw-sit-sit is a polymineralic rock rather than a single-mineral gem species, and its gemmological behaviour reflects that mixed composition.
Composition and structure
Kosmochlor — the dominant mineral in most maw-sit-sit — is the chromium analogue of jadeite, with the chromium replacing the aluminium of jadeite to give a deeper, more saturated green colour. The rock typically shows a bright chrome-green ground penetrated by darker green and black veining, the result of variable kosmochlor-jadeite-chromite distributions through the rock. Some specimens show whitish patches of albite and other lighter zones; others are nearly uniform deep green with finely distributed dark veining.
The rock is metamorphic in origin, formed under high-pressure low-temperature conditions in the same subduction-related setting as the Myanmar jadeite. The chromium that distinguishes maw-sit-sit from common jadeite is presumed to derive from chromite-bearing ultramafic rocks incorporated into the metamorphic protolith.
Gemmological properties
Hardness of maw-sit-sit is generally reported as 6 to 7 on the Mohs scale — softer than pure jadeite (about 7) and reflecting the polymineralic composition. Specific gravity ranges from approximately 2.8 to 3.4, again varying with the mineral mix. Refractive index is in the 1.52-to-1.74 range as a spot reading, depending on which mineral the polariscope hits. The variability of these properties is itself a useful identification clue: a stone presenting itself as jadeite that returns inconsistent gemmological readings on different parts of the same surface may be maw-sit-sit.
Identification and disclosure
The major laboratories — GIA, GAA, SSEF, and Gübelin — identify maw-sit-sit and report it accurately as a kosmochlor-bearing rock rather than as jade. The trade-disclosure question is whether the material is being sold as maw-sit-sit (which is honest) or as jade or jadeite (which is not, except in the loosest commercial sense). Reputable retailers list the material under its proper name and reserve the jade designation for true jadeite or nephrite.
The visual similarity to fine green jadeite is real enough that maw-sit-sit can be marketed deceptively to buyers who do not know the distinction. The dark veining characteristic of maw-sit-sit is the most reliable visual cue at the cabochon level, but verification by laboratory testing is the only certain identification.
In the trade
Maw-sit-sit is cut as cabochons, beads, and ornamental carvings rather than faceted stones, reflecting both its opaque-to-translucent nature and the carving traditions of the Myanmar jade trade. Prices are well below those of fine jadeite — orders of magnitude below imperial-jade prices — but above those of common chrome-green serpentine and similar substitutes. The material has a small but established place in the carved-stone and ornamental market and is recognised by serious collectors of Burmese material.
Cutting and care
Cabochon cutting follows the kosmochlor distribution, with the cutter orienting the stone to maximise the bright chrome-green areas in the dome. Hardness at 6 to 7 is sufficient for general jewellery use with reasonable care. Cleaning is by mild soap and warm water; the polymineralic composition makes ultrasonic and steam cleaning inadvisable.