mangelin

noun1

1. •
   (India, no longer used) A weight used to weigh precious stones, weighing more than a carat, usually 1¾ carats.

   • The chief weight of Diamonds, is the Mangelin; it weighs five Grains and three fifths, and the Carat weighs only four grains, and five Mangelins make seven Carats. — 1687