'Assuredly the turquoise doth possess a soul more intelligent than that
of man. But we cannot be wholly sure of the presence of Angels in
precious stones. I do rather opine that the evil spirit doth take up
his abode therein, transforming himself into an angel of light, to the
end that we put our trust not in God, but in the precious stone; and
thus, perhaps, doth he deceive our spirits by the turquoise: for the
turquoise is of two sorts: those which keep their colour, and those
which lose it.'[1]

[Footnote 1: 'Assurément la turquoise a une âme plus intelligente que
l'âme de l'homme. Mais nous ne pouvons rien establir de certain
touchant la presence des Anges dans les pierres precieuses. Mon
jugement seroit plustot que le mauvais esprit, qui se transforme en
Ange de lumiere se loge dans les pierres precieuses, à fin que l'on ne
recoure pas à Dieu, mais que l'on repose sa creance dans la pierre
precieuse; ainsi, peut-être, il deçoit nos esprits par la turquoise:
car la turquoise est de deux sortes, les unes qui conservent leur
couleur et les autres qui la perdent.' _Anselm de Boot_, Book II.]

'You thus see,' resumed Zaleski, 'that the turquoise was believed to
have the property of changing its colour--a change which was
universally supposed to indicate the fading away and death of its
owner. The good De Boot, alas, believed this to be a property of too
many other stones beside, like the Hebrews in respect of their urim and
thummim; but in the case of the turquoise, at least, it is a
well-authenticated natural phenomenon, and I have myself seen such a
specimen. In some cases the change is a gradual process; in others it
may occur suddenly within an hour, especially when the gem, long kept
in the dark, is exposed to brilliant sunshine. I should say, however,