Burma, jade, gems

Further investigation of maw-sit-sit, a vivid green ornamental stone from northern Burma, identifies its colouring constituent as a chromium-rich alkali pyroxene dispersed through a predominantly albite groundmass and leads to the proposed descriptive name jade-albite. Earlier examination had established the rock’s albite-rich composition but failed to identify the extremely small green pigment grains because they could not be adequately separated for chemical or X-ray analysis. Electron microprobe examination of a polished specimen demonstrates that chromium and iron are concentrated in the pigment rather than the surrounding albite. The reported chromium-to-iron ratio is approximately 3:1, with silicon also abundant and smaller quantities of titanium, calcium, and potassium detected. The article explains the principles and capabilities of electron-probe analysis, emphasizing its value for examining minute constituents in heterogeneous rocks. Although the initial measurements narrow the identification to a chromium-bearing pyroxene related to jadeite or aegirine, the grains remain too small for a satisfactory quantitative analysis. Improved concentration is achieved by grinding the rock to particles smaller than 10 micrometres and centrifuging them in a heavy-liquid mixture with a density of 2.75. The resulting sediment is substantially greener than either the original material or the lighter fraction. Comparative X-ray powder diffraction places the pigment within the alkali-pyroxene group, with lattice spacings intermediate between those of jadeite and aegirine. Partial chemical analysis of an approximately 70 per cent pigment concentrate yields about 10 per cent Na₂O, 7 per cent Cr₂O₃, and 4 per cent Fe₂O₃. Allowing for residual albite and possible iron contamination during preparation, Gübelin estimates that the pigment contains approximately 10 per cent Cr₂O₃ and constitutes roughly 20–25 per cent of the rock. He interprets it as jadeite in which substantial aluminium is replaced by chromium and iron, represented approximately by Na(Al,Cr,Fe)Si₂O₆, and proposes the name chrome-jadeite. Complete chemical characterization remains unattained because the minute, intimately intergrown crystals cannot be isolated in sufficient purity. The nomenclatural conclusion distinguishes the composite ornamental rock from jadeite itself, chloromelanite, and epidote: its dominant constituent is albite, while its striking colour arises from disseminated chrome-jadeite. Jade-albite is therefore recommended as a mineralogically informative designation, with maw-sit-sit retained as an acceptable local name.