Matura diamond

or Ma·ta·ra dia·mond

[ mah-ter-uh, mat-er-uh ]
/ ˈmɑ tər ə, ˈmæt ər ə /

noun Jewelry.

a zircon heat-treated to render it colorless: not a true diamond.

Origin of Matura diamond

First recorded in 1875–80; after Matura, town in Sri Lanka