opalize

from The Century Dictionary.

• To cause to resemble opal or to assume its structure or appearance: as, opalized wood. Also spelled opalise.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To convert into opal, or a substance like opal.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb To convert into a form of opal or chalcedony, especially to convert wood into such a fossilized form.
• verb To make opalescent.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb replace or convert into opal
• verb make opalescent