From the “gates of pearl” through which Saint Peter allows the elect to enter Heaven, to the guardians—“of Orient pearl a double row”—of the smiling mouth, the pearl has been caught into proverb and poem. At the beginning of this century, the pearl figured in a popular song: The hours I’ve spent with you, dear heart, Are as a string of pearls to me; I count them over, every one apart, My rosary. For some reason, all of Shakespeare’s references to the pearl are linked with sadness. The song in _The Tempest_ tells: Full fathom five thy father lies, Of his bones are coral made; Those are pearls that were his eyes ... And it is after Othello has killed his faithful wife Desdemona and has discovered that his clouding suspicions were untrue, that he calls himself: One whose hand, Like the base Indian, threw a pearl away Richer than all his tribe. As far back as the Bible a thing of supreme quality was referred to as a pearl of great price; and the same book (_Matthew_) issues the famous warning: “Neither cast ye your pearls before swine.” In other ways the pearl has been used as a symbol. The poet Swinburne, in sentimental mood, exclaimed: The world has no such flowers in any land, And no such pearl in any gulf the sea, As any babe on any mother’s knee. The rarity of the stone, and the difficult task of the pearl-diver, are used symbolically in an epigram by Dryden: Errors, like straws, upon the surface flow; He who would search for pearls must dive below. The American poet, William Russell Lowell (father of the Supreme Court Justice of the same name), wrote in his copy of the _Rubaiyat_ of Omar Khayyam: These pearls of thought in Persian gulfs were bred, Each softly lucent as a rounded moon; The diver Omar plucked them from their bed, Fitzgerald strung them on an English thread. _Other Stones_ The other stones, though less esteemed in lore and letters, have many claims to beauty. One shining specimen may adorn a jewel; or several of a kind, or combinations of various stones, may create effects that rival those of the gems. The four native stones among the five gems are usually translucent, while most of the other stones are opaque. A transparent or translucent stone, if it is cut as a prism or if its crystalline structure is right, may break light into rainbow hues, and, catching these rays, may shoot them around in varying interplays of sparkle and color. The opaque stones, on the other hand, often smooth of surface, are colored in ways that seem to snare the light and send it out with added power and color. Special characteristics add to the beauty of many of these stones, the main varieties of which we shall now glance at, in alphabetical order. _Agate_