The Steampunk Tritium Pendant. Featuring a brass chain and toughened glass. This pendant will glow for decades, literally.        Tritium has a half-life of 12.3 years, meaning after 12.3 years the pendant will glow half as bright, and after 24.6 years will glow a quarter as bright.   Tritium costs $30,000 per gram, putting it in the top 10 most expensive materials in the world (obviously it's in gaseous form in our pendants). It also has a half-life of 12.3 years, meaning after 12.3 years the pendant will glow half as bright, and after 24.6 years will glow a quarter as bright.