Quartz porphyry

Japanese: 石英斑岩 - せきえいはんがん（英語表記）quartz-porphyry

A rock with phenocrysts of quartz and alkali feldspar, usually orthoclase, which may contain mica. The groundmass is cryptocrystalline or microcrystalline. When the amount of phenocrysts is very large, it progresses to granite-porphyry, while when the amount of phenocrysts is small, it becomes quartz felsicite or microgranite. Early European petrologists classified extrusive rocks equivalent to granite, Tertiary and pre-Tertiary rocks as quartz porphyry, and rocks of later period as rhyolite [Tomkeieff: 1983]. Hornstone-porphyry [Cotta: 1862].

Source: Asakura Publishing Dictionary of Petrology Information

Japanese:

石英とアルカリ長石の斑晶をもつ岩石で，斑晶は一般に正長石で，雲母を含む場合もある．石基は潜晶質または微結晶質である．斑晶の量が非常に多くなると花崗斑岩（granite-porphyry）に移行する．一方斑晶が少なくなると石英珪長岩または微花崗岩となる．初期の欧州の岩石学者は花崗岩に相当する噴出岩で第三紀および先第三紀の岩石を石英斑岩とし，第三紀以後の岩石を流紋岩とした［Tomkeieff : 1983］．ホルンストーン斑岩（hornstone-porphyry）［Cotta : 1862］．

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