OP says it's an Edwardian opal and diamond brooch (except that I think it's more art nouveau...it's still gorgeous though!)
Style No. 114923 ~ Tensi chiffon full A-line gown with hand-beaded lace elbow-length sleeves, Queen Anne neckline, lace empire bodice features center gathered chiffon midriff accented with jewels and keyhole back, gathered skirt with sweep train, suitable as a mother of the bride dress or a formal gown.
~Bluebells~ Attract Hummingbirds ~Plant with Flowering Dogwood Tree which attracts Downy Woodpeckers.
Nature is one of God's good gifts. Isn't this amazingly beautiful? Love, love, love!