sentence: Iridium belongs to a group of metals known as transition metals.
sentences_before: Iridium is a metal. It is very hard to find and costs a lot.
sentences_after: It looks like platinum and is found in asteroids and comets. It can be used to find out when an asteroid or comet will hit the Earth. It is a very costly metal that can fold and bend just like aluminum. It is very shiny. It is relatively rare on the Earth's crust.
concept_name: iridium
headings: Iridium
categories: Chemical elements