Is a diamond a gemstone?

A diamond is a gemstone, and by most gemological standards it ranks as the hardest and most optically brilliant of the four classical precious stones. The gemstone category is defined by three criteria: durability, rarity, and a hardness threshold. Only diamond, emerald, sapphire, and ruby satisfy all three, with diamond scoring a 10 on the Mohs scale, the highest of any natural mineral. Lab-grown diamonds share this identical crystal structure and hardness, so they qualify as gemstones by the same criteria. The distinction that matters for buyers is origin, not classification: IGI-certified lab-grown diamonds carry the same four Cs grading as their mined counterparts. If you are comparing stones for a ring or pendant, the gemstone status of a lab-grown diamond is not a variable. What does vary is price per carat, which runs significantly lower for lab-grown, and traceability, which is clearer.