The hardest and most brilliant of gems, very rare and costly. The largest diamonds known in the world, procured from India and Brazil, are guarded among the royal treasures of England, Russia, etc., and valued at immense sums. Common diamonds are used not only for ornaments, but for cutting and graving hard substances, Jeremiah 17:1 . The Hebrew word here used is called "adamant" in Ezekiel 3:9 Zechariah 7:12 . See Exodus 28:18 39:11 Ezekiel 28:13 , and thought by some to mean the topaz. The diamond is carbon in its purest and crystalline form.