noun
conchoidal fracture
Technical term in geology and materials science for a curved, shell-like fracture surface, typical of glass and some minerals.
黒曜石は貝殻状断口を示す。
Obsidian exhibits a conchoidal fracture.
Compound of 貝殻 (seashell) + 状 (-shaped) + 断口 (fracture surface), describing the shell-like curved fracture pattern.