Chinese Turquoise Smooth Polished Round Ball Beads Strand Length is 18 Inches and Size 9.5mm to 12mm Approx.Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue.