Please use this identifier to cite or link to this item: https://ir.swu.ac.th/jspui/handle/123456789/15093
ชื่อเรื่อง: The origin of the green color of variscite
ผู้แต่ง: Calas G.
Galoisy L.
Kiratisin A.
Keywords: color
crystal chemistry
mineralogy
variscite
วันที่เผยแพร่: 2005
บทคัดย่อ: The color of variscite from three different localities (Pannecé, France; Sarrabus, Sardinia; Ervedosa, Portugal) and metavariscite from Utah was investigated by diffuse reflectance and EPR spectroscopy. These samples contain low levels of transition elements such as V, Cr, and Fe, the relative concentration of which varies with origin, although they remain in the wt% range. The presence of peculiar antiresonance features indicates that octahedral Cr3+ ions are responsible for the absorption bands that cause the green coloration of variscite and metavariscite. Trivalent iron ions, which give only a weak absorption band in some samples, and V3+ ions do not contribute to the green coloration of the samples from these locations. The crystal-field splitting and B Racah parameter of Cr3+ in variscite and metavariscite are 1590 and 657 cm-1 and 1610 and 575 cm-1, respectively. These values indicate a weak crystal field and an important Cr-O covalence. Electron paramagnetic resonance spectra show the presence of minor amounts (300-500 ppm) of vanadyl groups substituted for Al. The absence of V3+ indicates that variscite and metavariscite formed in an oxidizing environment.
URI: https://ir.swu.ac.th/jspui/handle/123456789/15093
https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444465983&doi=10.2138%2fam.2005.1668&partnerID=40&md5=5a18b13a7f8ab934939b50d9816319fb
ISSN: 0003004X
Appears in Collections:Scopus 1983-2021

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