The details of the expansion will vary according to the point and purpose of the metaphor. Thus, when Macbeth (act iii. sc. 1) says that he has "given his eternal jewel to the common enemy of man," the point of the metaphor is apparently the pricelessness of a pure soul or good conscience, and the metaphor might be expanded thus-- "As a jewel is precious to the man who wears it, so is a good conscience precious to the man who possesses it." But in Rich. II. i. 1. 180, the same metaphor is expanded with reference to the necessity for its safe preservation :--
A jewel in a ten-times barr'd-up chest Is a bold spirit in a loyal breast.