24th Anniversary
gemstone: Tanzanite.

Quick answer

The 24th anniversary gemstone is Tanzanite. The 24th anniversary traditional gift is musical instruments — the soundtrack of a marriage, from the wedding first-dance to the car radio to the child practicing piano. Tanzanite, the modern stone, adds its own once-in-a-generation story. In July 1967, a Masai tribesman named Ali Juuyawatu and a Goan tailor-turned-gold-prospector named Manuel de Souza independently discovered blue-violet zoisite crystals at the foot of Mount Kilimanjaro in Tanzania. Initially mistaken for sapphire, the material was identified as a new gem variety, and in 1968 Tiffany and Co. named it tanzanite after its single source country and marketed it as the gemstone of the 20th century. That source is still the only one on Earth — a four-kilometer strip of the Merelani Hills — making tanzanite roughly a thousand times rarer than diamond by geologist estimates, with the deposit expected to deplete within decades. Most market tanzanite is heat-treated (around 500-600 degrees Celsius) to remove brownish tones and bring out the blue-violet; the treatment is permanent and universally accepted. At Mohs 6.5-7 with moderate toughness, tanzanite wants protective settings. Fine AAA-grade runs $200-350 per carat at 1 carat, $500-675 above 3 carats — the luxury look of sapphire at a fraction of the cost. Twenty-four years, the eve of silver, gets the gem that Tiffany called a one-generation stone.