Pitchblende - Pitchblende (English spelling)

A variety of uraninite with no specific crystal morphology and a pitch-like appearance. It has a lower specific gravity and a higher impurity content, especially water, than typical uraninite. It is found in the form of a mass, or in the form of a breast- or kidney-like colloform structure (a structure in which fine particles are deposited in concentric rings or stripes) formed by the accumulation of layers with a striped structure. This type of appearance has a low degree of crystallinity. It occurs in relatively low-temperature pluton hydrothermal deposits and sedimentary rocks.

[Akira Kato]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

特定の結晶形態をもたない、ピッチ様の外観をもった閃ウラン鉱(せんうらんこう)の変種。典型的な閃ウラン鉱と比べて比重が小さく、不純物、とくに水の含有量が高い。塊状のものと、縞(しま)状構造を呈する層が集積してその表面が乳房様、腎臓(じんぞう)様のいわゆるコロフォーム構造（微粒子が同心円・縞状に沈積した組織）をもつものとがある。この種の外観のものは結晶度が低い。比較的低温の深成熱水鉱床や堆積(たいせき)岩中などに産する。

［加藤　昭］

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