Gehlenite (English spelling)

Japanese: ゲーレナイト（英語表記）gehlenite

A type of melilite with the chemical composition Ca ₂ Al ₂ SiO ₇ , it forms a solid solution with akermanite. It has a tetragonal crystal system. It is short columnar. It is colorless, gray-green, or brown. Its Mohs hardness is 5-6. Its specific gravity is 3.038. It gelatinizes with hydrochloric acid. There is an order-disorder phenomenon in the arrangement of Al/Si, and it violates the exclusion rule of Al. It undergoes a phase transition at 1000°C and 100 kbar or more, changing into a phase with the highest density of 4.426 g/cm3 of any silicate mineral. It occurs in contact metamorphic rocks, basic volcanic rocks, and meteorites, and also occurs in slag, but it is a rare mineral in Japan.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

メリライト(黄長石)の一種で，化学組成Ca₂Al₂SiO₇をもち，オケルマナイトと固溶体を形成する鉱物。正方晶系。短柱状。無色，灰緑，褐色。モース硬度5～6。比重3.038。塩酸によりゼラチン化する。Al/Siの配列に秩序‐無秩序現象があり，Alの排除則を破っている。1000℃，100kbar以上で相転移し，ケイ酸塩鉱物としては最高の密度4.426g/cm3の相に変わる。接触変成岩，塩基性火山岩，隕石に産し，鉱滓中にも生じるが，日本ではまれな鉱物である。

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