Terellian diamond

From Memory Alpha, the free Star Trek reference.

Terellian diamonds are precious but rare gemstones of Terellian origin.

In 2375, Benjamin Sisko enlisted Quark to help him procure Terellian diamonds for his wedding ring to Kasidy Yates. Quark was able to purchase a ring made with the diamonds, though he insisted that it was non-refundable because of the war with the Dominion. (DS9: "'Til Death Do Us Part")