Which word in this excerpt from act II, scene IV, of Shakespeare's Twelfth Night is a reference to a color-changing gemstone, hinting at Orsino's inconsistent nature?
CLOWN: Now, the [melancholy] god protect thee; and the
tailor make thy[ doublet] of changeable[ taffeta,] for
thy mind is a very [opal.] I would have men of such
[constancy] put to sea, that their business might be
every thing and their intent every where; for that's
it that always makes a good voyage of nothing. Farewell..
CLOWN: Now, the [melancholy] god protect thee; and the
tailor make thy[ doublet] of changeable[ taffeta,] for
thy mind is a very [opal.] I would have men of such
[constancy] put to sea, that their business might be
every thing and their intent every where; for that's
it that always makes a good voyage of nothing. Farewell..