ZHENGZHOU/BRUSSELS — A diamond is forever but its chemical composition is just carbon, the fourth most abundant element in the universe.

Before being cut and polished to what may cost over $2,000 per carat -- one-fifth of a gram, or the weight of two grains of rice, diamonds have traditionally been mined from earth where they were forged in extreme pressure and heat over millennia.

But companies in China and elsewhere have mastered the technologies to manufacture them en masse in a matter of weeks or days, with the products practically indistinguishable from those mined from earth.

China, long a major consumer of mined diamonds, now has a realistic chance to become a supplier of man-made ones and shape the industry, analysts said, but the scenario for substitution -- when consumers become indifferent to provenance -- is far from certain and depends on public perception.