FernGully Vintage Native American RingVintage Native American Ring. Green turquoise develops when there is iron present, which is the case with most Nevada turquoise, while Blue turquoise develops when there is copper present, which is the case with most Arizona Turquoise. Made of Sterling Silver Measures 1 Inch Tall Adorned with Coral and Turquoise Stones Available in Size 6. 5 Handcrafted by Native American Artisan