JADE

 

"Jade" refers to more than one specific type of metamorphic rock.  The four categories of "jade" are:

    1) jadeitite (jadeite jade)

    2) nephrite/nephritite (nephrite jade)

    3) chromian jade (maw sit sit)

    4) serpentine jade (not really jade)

 

Samples of jadeite jade and kosmochlor jade from Burma are shown below.

 

 

Jadeitite (~6.2 cm across along the base) from the Jurassic of Burma.  The light brown-colored rim is a weathering rind.  Jadeitite (= jadeite jade) is a rare metamorphic rock composed of jadeite pyroxene (Na(Al,Fe)(Si2O6)).  Published research on Burmese jade generally indicates that the jadeitite rock masses formed by metasomatism of albitites (= plagioclase feldspar metamorphites) at the periphery of serpentinized mantle peridotite bodies.  The mantle peridotite was part of a subducting slab of Mesozoic-aged oceanic lithosphere that was emplaced upward and against southeast Asian continental lithosphere by obduction.

Geologic unit: Hpakan-Tawmaw Jade Tract, Hpakan Ultramafic Body, Naga-Adaman Ophiolite.

Metamorphic age: late Tithonian Stage, near-latest Jurassic, 147 m.y.

Locality: alluvial clast (placer jade) from unrecorded locality (possibly in the vicinity of Phakant), upper reaches of the Uyu River (Uru River), western Kachin State, Indo-Burma Range, northern Burma.

 

 

Jadeitite (closeup of above specimen, ~2.2 cm across) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.

 

 

Jadeitite (~8.0 cm across at its widest) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.  The light brown-colored rim is a weathering rind.  Same geology & age & general locality as first specimen above.

 

 

Kosmochlor jade ("maw sit sit") (8.0 cm across along the base) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.

Maw sit sit is a very rare, complex, polymineralic metamorphic rock.  Minerals reported in this material include chromite (metallic black, FeCr2O4), kosmochlor pyroxene (emerald green to dark green to black, NaCrSi2O6), chromian jadeite pyroxene (green, Na(Al,Fe,Cr)Si2O6), chromiferous arfvedsonite amphibole (green or gray, Cr-bearing NaNa2Fe5Si8O22(OH)2), symplectite (green, a finely-crystalline mineral mix of mostly chromian jadeite).  Reported matrix minerals include thompsonite zeolite, albite feldspar, or serpentine.

Maw sit sit formed under high pressure and low temperature conditions at the rim of serpentinized, chromiferous mantle peridotites.  The peridotites were emplaced by obduction as oceanic lithosphere was subducting beneath the Burmese portion of southeastern Asia during the Mesozoic.

Geologic unit: northeastern end of the Hpakan-Tawmaw Jade Tract, Hpakan Ultramafic Body, Naga-Adaman Ophiolite.

Metamorphic age: late Tithonian Stage, near-latest Jurassic, 147 m.y.

Locality: apparently an alluvial clast derived from the Namshamaw Deposit ("Namshamaw Dike"; "Maw Sit Sit Vein") at Maw Sit Sit, just northwest of Namshamaw, near Kansi (Kanzi), western Kachin State, Indo-Burma Range, northern Burma.

 

 

Kosmochlor jade ("maw sit sit") (3.15 cm across at its widest) from the northeastern Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.  Same geology & age & locality as the first maw sit sit sample above.

 

 

Kosmochlor jade ("maw sit sit") (closeup of above specimen, 1.65 cm across) from the northeastern Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.

 

 

Jadeitite (lavender jadeitite) (18.2 cm across at its widest) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.  The light brown-colored rim is a weathering rind.  Lavender is a scarce color variation seen in Burmese jadeitites.  Whitish and near-white jadeite occurs throughout this rock, as well as hints of pale-greenish gray jadeite near the lower left edge.

Composition: the lavender color of the jadeite clinopyroxene (Na(Al,Fe)(Si2O6)) in this rock appears to be the result of ferrous iron to ferric iron (Fe+2 → Fe+3) intervalence charge transfer (Rossman, 1974).

Geologic Unit & Age & Locality: Same as the first specimen at top of page.

 

 

Jadeitite (lavender jadeitite) (closeup of above specimen, ~7.0 cm across) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma.

 

 

Jadeitite (lavender jadeitite) (closeup of above specimen, ~3.8 cm across) from the Hpakan-Tawmaw Jade Tract (near-latest Jurassic, 147 m.y.) of northern Burma showing lavender-colored jadeite, whitish to near-whitish jadeite, and hints of pale-greenish gray jadeite.

 

 

Some references on the geology of Burmese jadeitite and kosmochlor jade:

 

Rossman, G.R.  1974.  Lavender jade, the optical spectrum of Fe3+ and Fe2+ → Fe3+ intervalence charge transfer in jadeite from Burma.  American Mineralogist 59: 868-870.

 

Colombo, F., C. Rinaudo & C. Trossarelli.  2000.  The mineralogical composition of maw-sit-sit from Myanmar.  Journal of Gemmology 27(2): 87-92.

 

Shi G.H., Cui W.Y., Wang C.Q. & Zhang W.H.  2000.  The fluid inclusions in jadeitite from Pharkant area, Myanmar.  Chinese Science Bulletin 45: 1896-1901.

 

Kievlenko, E.Y.  2003.  Jadeite.  pp. 288-302 in  Geology of Gems, English Edition.  Ocean Pictures Ltd.  Littleton, Colorado.

 

Shi G.H., B. Stšckhert & Cui W.Y.  2005.  Kosmochlor and chromian jadeite aggregates from the Myanmar jadeitite area.  Mineralogical Magazine 69: 1059-1075.

 

Harlow, G.E., S.S. Sorensen & V.B. Sisson.  2007.  Jade.  in  Geology of gem deposits.  Mineralogical Association of Canada Short Course Series 37: 207-253, pls. 9-1 to 9-7.

 

Qiu Z.L., Wu F.Y., Yang S.F., Zhu M., Sun J.F. & Yang P.  2008.  Age and genesis of the Myanmar jadeite: constraints from U-Pb ages and Hf isotopes of zircon inclusions.  Chinese Science Bulletin 54: 658-668.

 

Shi, G.H., Cui W.Y., Cao S.M., Jiang N., Jian P., Liu D.Y., Miao L.C. & Chu B.B.  2008.  Ion microprobe zircon U-Pb age and geochemistry of the Myanmar jadeitite.  Journal of the Geological Society of London 165: 221-234.

 

Shi G.H., Jiang N., Liu Y., Wang X., Zhang Z.Y. & Xu Y.J.  2009.  Zircon Hf isotope signature of the depleted mantle in the Myanmar jadeitite: implications for Mesozoic intra-oceanic subduction between the Eastern Indian Plate and Burmese Platelet.  Lithos 112: 342-350.

 

Shi G.H., Wang X., Chu B.B. & Cui W.Y.  2009.  Jadeite jade from Myanmar: its texture and gemmological implications.  Journal of Gemmology 31: 185-195.

 

Shi G.H., Jiang N., Wang Y.W., Zhao X., Wang X., Li G.W., E. Ng & Cui W.Y.  2010.  Ba minerals in clinopyroxene rocks from the Myanmar jadeitite area: implications for Ba recycling in subduction zones.  European Journal of Mineralogy 22: 199-214.

 

 

 

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