noun
porphyrite
A type of igneous rock with distinct larger crystals in a fine-grained matrix. Technical term used in geology.
この地域の地層にはひん岩が多く含まれている。
The strata in this area contain a lot of porphyrite.
From Chinese 玢岩 (bīnyán), a geological term for porphyrite. The kanji 玢 is rare and often replaced by ひん in modern Japanese.