From Elite Wiki

A commodity found on the F8 markets screen.

Traded in kilogrammes (like Platinum), and hence kept in the ship's safe - and thus salvageable when you blast off in your Escape Pod!

Often much cheaper if bought at Rock Hermits, often more expensive at luxurious systems (eg high TL corporate states).

If have added OXPs with luxury dockables such as Liners, the markets there are often even better - especially if they are visiting a luxurious system - but their markets tend to be limited, and can be suicidal to dock at!