Mineral identification of black-jade gemstone from Aceh Indonesia

One of the gemstones in Aceh Indonesia is called black-jade where the name of black-jade is a local name. Unfortunately, detail information about this gemstone is still limited. No one knows whether this gemstone can be categorized as jade or not until this study is presented. We have utilized X-Ray Fluorescent (XRF) to study the black-jade gemstone from Aceh Tengah (Takengon) and Nagan Raya regions in Indonesia. Our results show that the black-jade gemstone from Aceh Tengah contains 39.6% of SiO₂, 35% of Fe₂O₃, 17% of MgO, 3% of CaO, and 2% of NiO. While, the black-jade gemstone from Nagan Raya contains a little bit less SiO₂ but more Fe₂O₃ than that of black-jade from Aceh Tengah: 38.4% of SiO₂, 39% of Fe₂O₃, 17% of MgO, 0.5% of CaO, and 2.6% of NiO. By comparing the results to the available mineral data (jadeite, nephrite-actinolite, nephrite-tremolite, serpentine-clinochrysotile, serpentine-antigorite, and vesuvianite), we found that oxide compounds contained in the black-jade gemstone from Aceh are found in the serpentine-antigorite, except H₂O. The total difference between the oxide compositions in black-jade and serpentine-antigorite is 43% with its average difference of 11%. This means that the oxide composition in black-jade is almost the same as in the serpentine-antigorite. Accordingly, the black-jade gemstone from Aceh Indonesia is a type of serpentine-antigorite-jade.