'Pearl' in the Bible

lading of gold, and silver, and precious stone, and pearl, and fine linen, and purple, and silk, and scarlet, and all thyine wood, and every vessel of ivory, and every vessel of most precious wood, and brass, and iron, and marble,

And the twelve gates are twelve pearls, each several one of the gates was of one pearl; and the broad-place of the city is pure gold -- as transparent glass.