This indiscriminate use of the gem's name to appropriate its pearly characteristics is a common poetic license. In Ben Jonson's "Hymn to Diana," he bids her,
Lay thy bow of pearl apart.
Sometimes metaphor is worse mixed, as when Milton in "Paradise Lost" describes the waters above the firmament about the gate of Heaven thus:
And underneath a bright sea flowed
Of jasper, or of liquid pearl.
In this poem of gorgeous description, the author makes several allusions to the gem and some of them, especially those in his word paintings of scenes in Eden, are poetically beautiful and true. One delightful to the eye of the mind,
How from that sapphire fount the crispèd brooks
Rolling on orient pearls and sands of gold,
and another in the description of morning in Eden, equally beautiful though it takes more license:
Now Morn, her rosy steps in th' eastern clime