1/4 CT TW Lab Grown Diamond 18K Gold Over Sterling Silver Baguette Necklace; Chain Length 18" + 2" Extender. These lab grown diamonds are guaranteed to be of the highest quality and also include certification from the International Gemological Institute (IGI). Lobster closure, 1 Polished finish China Imported Product Specifications 18" + 2" Material & Care Metal, Sterling silver Clean with a soft bristle brush or cloth and warm soapy water.