Star K Large Solitaire Big Stone Ring 10mm Round Simulated Tanzanite Sterling Silver Metal: 925 Sterling Silver. Dimensions: Width: 10.00 This beautiful design is part of the exclusive Star K. Jewelry collection. Star K, is a reputable American Family Business based in New York since 1986, uses only the highest quality materials, and will proudly stand behind all of her products. Simulated Tanzanite: The Simulated Alternate Birthstone for September. Tanzanite is a rare blue gem and a popular alternative to blue sapphire. The gemstone was discovered in 1967, and it is mined at only one very small mining location in Tanzania. Additional Stones: