自然 しぜんルテニウムじゃなかったです
shizen rutenyūmujanakattadesu

Noun
Desu Copula

The polite, past negative form of 自然ルテニウム

1. Wasn't natural ruthenium.; Wasn't naturally occurring ruthenium.

Past/Perfective
Negative
Polite
Casual Register
Geology