This is a round-cut crystal necklace top made of 750 WG. It is stamped 0.415ct. =Product Size= Material: K18 white gold, blue diamond Stone: 1 blue diamond, approximately 5mm in diameter, 0.415ct Size: Top: Approximately 7.5mm long x 5.0mm wide, 4.5mm deep I'm not sure if it's treated or natural, but it sparkles and shines beautifully. It was purchased at Sasaki Watch Shop. Chain not included. Please use your own. It is often mistaken for blue zircon, but this is a diamond, so it has the genuine sparkle of a real diamond. *I am hesitant to list it, so there is a possibility of deletion or price increase. k18 18k gold pure gold pendant asset 0.3ct 0.4ct 0.5ct Price revised due to rising gold prices.