Although Solinus, writing in the third century A.D., relies mainly upon Pliny for his information on precious stones, still he here and there gives evidence of a more critical spirit, as when he says of the rock-crystal that the theory according to which it was frozen and hardened water was necessarily incorrect, for it was to be found in such mild climates as “Alabanda in Asia and the island of Cyprus".[16] This is the more notable that the wholly incorrect view persisted into the sixteenth century, so learned a writer as Lord Bacon (d. 1626) restating it in his last work, “Sylva Sylvarum”.

[Footnote 16:  Collectanea rerum memorabilium, Cap. 15.]

One of the most curious gem-treatises, especially as a source of early sixteenth-century beliefs in the magic properties of precious stones, the “Speculum Lapidum” of Camillo Leonardo, published in Venice, 1502, probably never came under Shakespeare’s eye.  Indeed, even in Italy it seems to have been so neglected that Ludovico Dolci ventured to publish a literal Italian version of the Latin original as his own work in 1565.  The English “Mirror of Stones”, issued in 1750, is frankly stated to be a translation of the Latin original bearing the same name.[17]

[Footnote 17:  Noted in the present writer’s “The Curious Lore of Precious Stones”, Philadelphia and London, 1913, p. 18.]

In Marlowe’s (1564-1593) “Hero and Leander”, almost certainly written before Shakespeare’s “Venus and Adonis” (1593), although not published until 1598, five years after Marlowe’s death, “pearl tears” and the “sparkling diamond” are used much in the same way as by Shakespeare, as appears in the following verses: 

Forth from those two translucent cisterns brake
A stream of liquid pearl, which down her face
Made milk-white paths. 

          
                                                                Lines 296-298.

Why should you worship her! her you surpass
As much as sparkling diamonds flaring glass. 
Lines 213,214.

There is a curious parallelism between a passage in Troilus and Cressida, 1609, and one in Marlowe’s Dr. Faustus, 1588.  Marlowe wrote (sc. 14, l. 83): 

Was this the face that launched a thousand ships
And burnt the topless towers of Ilium?

This is followed very closely by Shakespeare, with the substitution of “pearl” for “face”.

She [Helen] is a pearl,
Whose price hath launch’d above a thousand ships.
Troilus and Cressida, Act ii, sc. 2, l. 82. 
First Folio, at end of “Histories”, unnumbered page
(596 of facsimile), col.  A, line 19.

The greatest of the world’s poets lived in a period midway between the highest development of Renaissance civilization and the foundation of our modern civilization, and he was thus at once heir to the rich treasures of a glorious past, and endowed with a poetic, or we might say a prophetic insight that makes his works appeal as closely to the readers of to-day as to those of his own time.