@Bob (totally off-topic for anyone not interested)
Wilkie Collins (1824 - 1889) was an English novelist, most famous for his works 'The Woman in White' and the history-making 'The Moonstone' -- which is, arguably, considered the first detective novel to be written in English.
Though the gem in the story was actually a diamond, true moonstones experienced a huge surge in popularity, based on the title of Wilkie's serial, and are still popular today.
Moonstones are lovely, and similar to opals. A quick search of 'moonstone jewelry' via Google images, might just make you fall in love . . . with the gleaming, mysterious, moonstone! :-)