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Caldasite
Caldasite ((ドイツ語:Caldasite) (スペイン語:Caldasite)) is a very rare uraniferous zirconium ore, composed of ZrSiO4, ZrO2 (baddeleyite; over 60%), and U3O8. This complex ore is primarily found in the region of Pocos De Caldas, Minas Gerais, Brazil (hence the name ''caldasite''). Caldasite is very heavy and is mostly ashy in color, usually varying between green, brown, and red. Because it contains valuable minerals, caldasite can be used to salvage zirconium ore and is a source of baddeleyite for industrial uses, although it can be considered a health hazard for its tendency to have low-level radioactivity.
== Composition ==
The formation of caldasite is the combined mixtures of zirconium (ZrSiO4), baddeleyite (ZrO2, named after Joseph Baddely, who first introduced the Sri Lankan material). (ZrO2) and uranium (U3O8). On the cleavage faces of polished crystals color zones of varying widths are accentuated, and on these faces the crystals show various iridescent colors. In transmitted light they are strongly colored. Within the internal structure they are fractured and full of cavities. The gray "combs" with the earthy fracture of caldasite are shown by x-rays to be isotropic, opaque, and amorphous. "The dark brown, nearly black "combs," called "zirkonglaskoepfe" (zircon glass-heads) by the German authors differ little in composition from the amorphous material. A spectrochemical analysis of the specimen showed that the substance contained some manganese. This was chemically determined to be of the order of one part in twenty thousand, and in part maybe accountable for its coloring. Table 1 lists the nominal composition of caldasite ore.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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