E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Heliotrope (4 syl.).
Apollo loved Clytie, but forsook her for her sister Leucothoe. On discovering this, Clytie pined away; and Apollo changed her at death to a flower, which, always turning towards the sun, is called heliotrope. (Greek, turn-to-sun.)
According to the poets, heliotrope renders the bearer invisible. Boccaccio calls it a stone, but Solnus says it is the herb. Ut herba ejusdem nominis mixta et prcantationibus legitimis consecrata, eum, a quocunque gestabitur, subtrahat visibus obviorum. (Georgic, xi.)
No hope had they of crevice where to hide,
Or heliotrope to charm them out of view.
Dante: Inferno, xxiv.
The other stone is heliotrope, which renders those who have it invisible.Boccuccio: The Decameron, Novel iii., Eighth day.