Silver Is Soft Like Gold, Which Is Why It Is Alloyed Too

Silver shares its FCC crystal structure with copper and gold, covered on their own materials science pages, and with it, the same high-ductility, comparatively low-hardness mechanical character. Pure silver jewellery or flatware would scratch and deform quickly in ordinary use, the same problem gold solves with karat alloying, covered on gold’s mechanics page.

Sterling silver as the real-world fix

\text{Sterling} = 92.5\%\ Ag + 7.5\%\ Cu

Sterling silver's defining composition. The added copper, like the copper or silver added to karat gold, distorts silver's FCC lattice locally and resists the dislocation motion that lets pure silver deform so easily, a real, measurable hardening effect.

92.5%

Silver content in sterling silver

7.5%

Copper content

the hardening addition

FCC

Shared structure with copper and gold

Why this is the same mechanism, a different ratio

Sterling silver’s 7.5% copper addition is a smaller fraction than even 18-karat gold’s 25% non-gold content, covered on gold’s mechanics page, reflecting silver’s own somewhat different baseline hardness and the specific durability target jewellers and silversmiths have settled on for flatware and jewellery over centuries of practical use.

Sources: sterling silver composition and alloy hardening mechanisms draw on standard jewellery metallurgy and materials science references.