Lead sulfide crystals are a Cybertronian food product, and are apparently delicious when combined with savory mercury sauce and flavorful iron filings as garnish for a tasty robot. They are, of course, poisonous and quite inedible for humans. The crystals found on Femax emit a greenish glow in the visible spectrum; this may indicate that they are formed from an unknown radioactive lead isotope. Lead sulfide additive appears to act as an anti-allergy remedy for some Transformers. Lightspeed must take some with his fuel or break out with a rust rash and other troubling symptoms.