Fun Fact: It is the only element that easily forms minerals with gold; most gold ore comes in the form of gold telluride. The radioactive isotope tellurium-128 has the longest known half-life of any known unstable isotope, at 2.2 septillion years, or 2.2X10^24 years. A small amount of tellurium, if spilled on the skin, makes you smell of garlic for weeks.