The agate is a variety of chalcedony. It is named from the river Achates, in Sicily. A hard stone, of striped or cloudy coloring, it is often yellow or tawny brown. Shakespeare in Romeo and Juliet uses the agate in a ring to indicate the size of Queen Mab, who—before Freud brought us other fancies—was the bringer of dreams:
She is the fairies’ midwife, and she comes
In shape no bigger than an agate-stone
On the forefinger of an alderman ...
In her coach, Queen Mab gallops by night
Through lovers’ brains, and then they dream of love;
O’er courtiers’ knees, that dream on curtsies straight;
O’er lawyers’ fingers, who straight dream on fees;
O’er ladies’ lips, who straight on kisses dream.