IIRC there are a lot of period 5 transition metals in asteroids which are rare on Earth because they're heavy and sank into the core during the planet's formati

IIRC there are a lot of period 5 transition metals in asteroids which are rare on Earth because they're heavy and sank into the core during the planet's formation. Specifically molybdenum, niobium, ruthenium, rhodium, palladium, and silver. Some of these have very interesting properties but the supply of all of them is pretty limited on Earth.