(Heb. gabish, Job 28:18; Gr. margarites, Matt. 7:6; 13:46; Rev. 21:21). The pearl oyster is found in the Persian Gulf and the Red Sea. Its shell is the “mother of pearl,” which is of great value for ornamental purposes (1 Tim. 2:9; Rev. 17:4). Each shell contains eight or ten pearls of various sizes.
Pearl
3 verses
Job
Job 28:18
No mention shall be made of coral, or of pearls: for the price of wisdom is above rubies.
Revelation
Revelation 17:4
And the woman was arrayed in purple and scarlet colour, and decked with gold and precious stones and pearls, having a golden cup in her hand full of abominations and filthiness of her fornication:
Revelation 21:21
And the twelve gates were twelve pearls; every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass.
From Easton's Bible Dictionary
Matthew George Easton, 1897