玄武岩 (Hiân-bú-giâm) (basalt) 是 (sī)1種 (chióng)火山巖 (hoé-soaⁿ-giâm) (volcanic rock),大份 (toā-hūn)烏 (o͘)烏抑 (ia̍h)爪鼠仔色 (niáu-chhí-á-sek)。火鍋 (Hoé-ko)佇 (tī)地表 (tē-piáu)真 (chin)緊 (kín)冷落來 (léng--lo̍h-lâi)就 (tō)會 (ē)造成 (chō-chiâⁿ)玄武岩。玄武岩有 (ū)相 (SiO)2 45~52%。結晶 (Kiat-chiⁿ)較 (khah)大 (toā)粒 (lia̍p)的 (ê)玄武岩算 (sǹg)1種斑岩 (pan-giâm) (porphyritic) 的結構 (kiat-kò͘)。嫌武岩 (Hiâm-bú-giâm)本身 (pún-sin)是烏的 (o͘--ê),伊 (i)的礦物 (khòng-bu̍t)成份 (sêng-hūn)大體 (tāi-thé)是斜塘石 (chhiâ-tn̂g-chio̍h) (plagioclase) 甘 (ham)輝石 (hui-chio̍h) (pyroxene),嘛 (mā)有少 (chió)少的橄欖石 (kan-ná-chio̍h) (olivine); 遮的 (chiah-ê)礦物予 (hō͘)嫌武岩有無 (bô)仝 (kâng)的特色 (te̍k-sek)。