Zenium

The purple substance zenium was mined in tunnels on Oovo IV. It was mined by using a gasifier, which turned rock into plasma and sucked it up a carbonite nanofiber tube to be vented into the atmosphere, and also a sonic tool, to chip the mineral out. The rock's fracture was roughly hexagonal, and its hardness must have been fairly high, due to the fact that a sonic tool was needed to remove it from the earth.

Zenium dust was known to cause a respiratory illness known as Firelung, which, in humanoids, destroyed alveoli like acid.

Zenium, strangely enough, made droids' perceptor systems malfunction to a degree where they would be walking into mining equipment and each other. This was the main reason only sentient beings were used to mine zenium. And, since zenium dust was deadly, only the criminals most resilient to reform were sent there for the ultimate punishment.

Text and facts from the “Zenium” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.