Vintage 80's Birks 10K yellow gold blue zircon

Vintage 80's Stamped Birks 10K yellow gold Marquis cut blue zircon. Approx 6.75 & 2g. Blue zircon is more expensive than blue topaz. Topaz is a naturally occurring mineral that comes in a variety of colors, but it doesn't come as close as zircon to mimicking the luster and fire of a diamond.