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石基

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The smooth texture of this basaltic volcanic bomb is aphanitic.

アファナイト（潜晶質岩）の特性と火成岩の分類

アファナイト潜晶質火成岩火山岩
2026年8月10日続きを読む →
IUGS classification of aphanitic extrusive igneous rocks to their relative alkali (Na2O + K2O) and silica (SiO2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot. Original source: *Le Maitre, R.W. (ed.); 1989: A classification of igneous rocks and glossary of terms, Blackwell Science, Oxford.

火山岩（噴出岩）の形成プロセスと多様な岩石タイプ

火山岩噴出岩マグマ斑晶
2026年8月10日続きを読む →
Porphyritic texture in a granite. This is an intrusive porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California.

斑状組織（ポルフィリティック）とは？火成岩の結晶サイズが異なる理由を解説

斑状組織ポルフィリティック斑晶石基
2026年8月9日続きを読む →
Granites often have large feldspathic phenocrysts. This granite, from the Swiss side of the Mont Blanc massif, has large white phenocrysts of plagioclase (that have trapezoid shapes when cut through). 1 euro coin (diameter 2.3 cm) for scale.

斑晶（Phenocryst）とは？火成岩の組織から読み解くマグマの履歴

斑晶火成岩斑状組織マグマ
2026年8月9日続きを読む →
IUGS classification of aphanitic extrusive igneous rocks to their relative alkali (Na2O + K2O) and silica (SiO2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot. Original source: *Le Maitre, R.W. (ed.); 1989: A classification of igneous rocks and glossary of terms, Blackwell Science, Oxford.

火山岩（噴出岩）の形成プロセスと多様な組織・種類

噴出岩火山岩マグマ斑晶
2026年8月9日続きを読む →