Conchoidal fracture is a curved fracture surface most notably seen in which substance?

• A. Glass
• B. Metal
• C. Wood
• D. Clay

Answer: (A)

Conchoidal fracture is a curved, shell-like fracture surface that forms when a brittle material lacks a crystalline structure, so cracks propagate in a smooth, rounded way rather than along flat cleavage planes. Glass is the classic example because it is an amorphous solid; when it breaks, the fracture surfaces are characteristic, smooth, curved, and sometimes show concentric ripples. Metals tend to fracture along cleavage or ductile paths with necking, wood breaks along grain, and clay crumbles rather than forming these curved surfaces. So the curved fracture surface most notably appears in glass.