Lovely Sky Blue Sapphire Gemstone from Montana, 0.56 cts., 4.7 mm., Round ShapeGem: Sapphire Weight: 0. 56 cts. Size: 4. 73 mm. Color: Sky Blue with Yellow Highlights Clarity: SI Cut: Round Brilliant Locality: Rock Creek, Granite Co., Montana Treatment: Heated One of the most sought after gemstones from the US is Sapphire. Montana is one of the largest producers of gem grade Sapphire rough in the world. Every color of Sapphire imaginable comes from the rivers of Montana! It has been producing Sapphire since the start of the 20th