Tanzanite is a rare and striking gemstone, known for its mesmerizing blue-to-violet tones, found exclusively in the Merelani Hills of Tanzania. Famous for its incredible rarity and vivid colour-shifting properties, it serves as a popular modern birthstone for December. Tanzanite celebrates 24 years of marriage. We would describe the colour as London Blue. The pear shaped Tanzanite, 1.4ct , is set in 18ct gold. Such a statement ring.