Figure 12. The UV-Vis spectrum of a blue sample from Itoigawa (K-IT-JP-16). The absorption shows a very wide broad band from 500 to 750 nm that overlaps the Mn-related broad bands at 530 and 570 nm observed in Burmese lavender jadeite. The chromophores Ti and Fe show a significant concentration at 1943 and 4212 ppma, respectively, and this jadeite’s blue color could be mainly due to the Ti4+-Fe2+ charge transfer.
Figure 11. Illustration of the atomic arrangement of a single-chain pyroxene crystal structure, from the a-axis to b-axis direction. In the SiO4 tetrahedrons (indicated in yellow and brown), four oxygen atoms surrounding a silicon atom are connected to form a strand, and other six-coordinate octahedron atoms (in green) are arranged so that they link the strands. Larger atoms (orange spheres) fill the spaces. Modified after Miyawaki (2004).
Figure 10. The UV-Vis spectrum of a lavender sample from Itoigawa-Omi (K-IT-JP-25). Two broad bands centered at 530 and 610 nm correspond to Mn and Ti-Fe charge transfer, and there is also a weak narrow band at 437 nm. The violet color reflects the chromophore combination of low Mn (18 ppma) and much higher Ti (534 ppma) and Fe (550 ppma).
Figure 9. The UV-Vis spectrum of a green sample from Itoigawa (K-IT-JP-14) shows the features corresponding to Cr- and Fe-bearing green jadeite: the characteristic narrow 691 nm absorption, two Cr3+-related weak shoulders at 650 and 630 nm, and a sharp, narrow absorption of Fe3+ at 437 nm. The saturated green area of the spectrum corresponds to the concentration of the chromophores Cr and Fe (280 and 810 ppma, on average).
Figure 8. A two-dimensional Raman spectroscopy mapping image of a jadeite boulder from Itoigawa. The red area corresponds to the jadeite distribution, the green area to dark green richterite (amphibole group), and the blue area to the mineral prehnite, which is located at the veinlet and crosses through the stone. The mapping area is 44 × 30 mm.
Figure 7. Petrographic microscope images of jadeite samples from Itoigawa. The left images are under plane-polarized light, the right images under cross-polarized light. Jd, Preh, Ves, An, and Ti indicate jadeite, prehnite, vesuvianite, analcime, and titanite, respectively. A1: Green jadeite K-IT-JP-14 shows a prismatic-granular crystalloblastic texture, a distribution of fine colorless cryptocrystalline grains of jadeite, and a predominance of grains around 0.05–0.3 mm in size. A2: Coarse pale green grains larger than 2 mm can also be observed in the same matrix, which is a well-formed large jadeite single crystal. The prominent (110) cleavage planes intersecting at 87° are characteristic of pyroxene. B1: Lavender jadeite K-IT-JP-25 shows near-colorless fine and micro-grained jadeite crystals with a prismatic crystalloblastic texture. B2: Ultramylonitic zones with radiating aggregates of fine jadeite grains cut randomly through the center of the matrix, indicating a lithostatic pressure during the metamorphic process. B3: Dark gray prehnite and analcime, the main constituents of the veinlets that cut through this lavender jadeite, were formed by hydrothermal fluids. A high-relief prismatic vesuvianite crystal was also found as a component mineral. C1: K-IT-JP-16 is a predominantly blue specimen, translucent with fine cryptocrystalline grains. C2: Crushed preexisting minerals produce a flow structure with granoblastic and mylonitic texture. The component minerals analcime and a very minor amount of euhedral titanite grains are observed in the matrix. Photomicrographs by Ahmadjan Abduriyim.
Figure 6. Left: A 4.6 ton jadeite rough boulder is displayed at the Fossa Magna Museum in Itoigawa. This eroded and rounded boulder from the Kotaki area is mostly white, with some green areas of jadeite; the fibrous structure in the black area is amphibole. Thin fault-like veins are filled with white minerals. Center: A 30 kg rounded boulder of predominantly lavender jadeite was found along the Hime River in Itoigawa. The lavender color is dispersed irregularly over the white matrix. Right: These rounded jadeite pebbles, found along the coast in Itoigawa-Omi, are approximately 2 to 15 cm long. Photos by Ahmadjan Abduriyim, courtesy of the Fossa Magna Museum and the Jade Ore Museum (Hisui Gensekikan).
Figure 7. Petrographic microscope images of jadeite samples from Itoigawa. The left images are under plane-polarized light, the right images under cross-polarized light. Jd, Preh, Ves, An, and Ti indicate jadeite, prehnite, vesuvianite, analcime, and titanite, respectively. A1: Green jadeite K-IT-JP-14 shows a prismatic-granular crystalloblastic texture, a distribution of fine colorless cryptocrystalline grains of jadeite, and a predominance of grains around 0.05–0.3 mm in size. A2: Coarse pale green grains larger than 2 mm can also be observed in the same matrix, which is a well-formed large jadeite single crystal. The prominent (110) cleavage planes intersecting at 87° are characteristic of pyroxene. B1: Lavender jadeite K-IT-JP-25 shows near-colorless fine and micro-grained jadeite crystals with a prismatic crystalloblastic texture. B2: Ultramylonitic zones with radiating aggregates of fine jadeite grains cut randomly through the center of the matrix, indicating a lithostatic pressure during the metamorphic process. B3: Dark gray prehnite and analcime, the main constituents of the veinlets that cut through this lavender jadeite, were formed by hydrothermal fluids. A high-relief prismatic vesuvianite crystal was also found as a component mineral. C1: K-IT-JP-16 is a predominantly blue specimen, translucent with fine cryptocrystalline grains. C2: Crushed preexisting minerals produce a flow structure with granoblastic and mylonitic texture. The component minerals analcime and a very minor amount of euhedral titanite grains are observed in the matrix. Photomicrographs by Ahmadjan Abduriyim.
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