A type of pyroxene, often light in color. It can be platy or columnar, or granular or fibrous. It is very common in metamorphic rocks of calcareous and dolomite origin, where it is associated with wollastonite, vesuvianite, cobaltite, forsterite, phlogopite, and scapolite. It also occurs in basic igneous rocks and syenite pegmatites. In addition to the cleavage characteristic of pyroxenes, it often has a well-developed split in one direction. This characteristic is particularly evident in the so-called heteroexfoliated pyroxenes. The English name is derived from the Greek word meaning "seeming two", probably due to the variety of crystal habits. [Satoshi Matsubara] [References] | | | | | | | | | | [Additional information] |Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend |
輝石の一種で、淡色調のことが多い鉱物。板状、柱状の結晶形をするほか、粒状や繊維状にもなる。石灰質、苦灰質岩起源の変成岩類に珪(けい)灰石、ベスブ石、灰礬(かいばん)ざくろ石、苦土橄欖(かんらん)石、金雲母(きんうんも)、スカポライト(柱石(ちゅうせき))などを伴い、きわめて普通に産する。塩基性火成岩中や閃(せん)長岩質ペグマタイト中にも産する。輝石特有の劈開(へきかい)のほかに、しばしば一方向によく発達した裂開がみられる。いわゆる異剥(いはく)輝石といわれているものはこの性質が顕著なものである。英名は、ギリシア語の二つに見えるという意味から由来する。おそらく種々の晶癖(しょうへき)をもっているためであろう。 [松原 聰] [参照項目] | | | | | | | | | | [補完資料] |出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例 |
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