Gemology And Mineralogical Study Of Guatemala Jadeite Jade Along The Motagua Fault Zone

The Motagua River of Guatemala follows the Motagua fault zone,the present plate boundary zone between the North American (Maya block) and Caribbean (Chortis block) plates.The central Motagua River valley is bordered by E-W-striking tectonic slices of serpentinite,some of which contain blocks of high pressure/low temperature(high P/T) eclogite,garnet amphibolite,and jadeite.Recent exploration for commercial jadeitite (jade) has discovered considerable quantities of high P/T rocks in serpentinite bodies both further along and farther from the river.The southern bodies,south of the Motagua fault zone and adjacent to Chortis basement,also contain abundant jadeitite,albitite,and garnet amphibolite,but rare eclogite. Mineralogical differences between jadeitites from the northern and southern bodies,and the different lithotectonic assemblages on the tow sides of the Motagua fault zone suggest that either tow high P/T events have occurred,or the tow belts may be a single unit disrupted by strike slip duplexing.In this paper, jadeite samples collected from Guatemala and Myanmar were studied by optical microscopy(OM),Electron probe analysis(EP), X-ray powder diffraction(XRD) and infrared spectroscopy(IR) on their mineral composition ,physical characteristics, structure and crystal structure of the major minerals.The Electron microprobe analysis shows that the main minerals in Guatemala jadeite are jade containing omphacite, albite, titanite, muscovite and so on and the chemical composition of jade in Guatemala is almost free of chromium. The Na20 content in Myanmar Jade significantly is higher than in Guatemala Jade, while the Al2O3 content in the areas of Myanmar Jadeite Jade is also slightly higher than that in the region of Guatemala. The FeO, MgO, MnO and CaO contents in Guatemala jadeite are higher than Myanmar jadeite, and these components in Myanmar jadeite are exetremely low. In the end-member component triangular diagram,we can known that the Ca, Mg and Fe contents is high in Guatemala jadeite, while the content of NaAl [Si2O6] is high in Myanmar jadeite.The main diffraction peaks in Guatemalan jadeite rock X-ray diffraction pattern is the main diffraction characteristic of jadeite, from which we can conclude that the main mineral is jadeite. There is a small amount of impurity peaks contain other minerals such as omphacite,and albite, which is consistent with the analysis reault of composition. By calculating its crystallinity, we can see the quality of jade in Guatemala is bad than Myanmar jade. Infrared spectroscopy showed 1063 cm-1, 473 cm-1, 573 cm-1, 743 cm-1 of the peak shape and peak graphics in the 400 cm-1-1600 cm-1 band and that is broadly consistent with the standard jadeite infrared map, which may be inferred that these peaks are of the infrared spectrum peak of jadeite.The main elements of the evaluation of Jade are: color, transparency, texture, clarity, process, volume six factors. The jade from Motagua River of mid-Guatemala shows unique blue-green, transparence is in the range of opaque to transparent, the micro-structure is coarse, the grain is visible to the naked eye and there are micro-cracks. Considering all the factors and comparing overall grade of jade ,we can concludes that the jade in Guatemala can only be used as carvings, the jade production in this area is low, the grade level is lower than Myanmar jade and the jade in Guatemala can not comparable with Myanmar jade as a whole.