fissile

1. (geology) Easily split along a grain.Examples: "This Cryſtal is a pellucid fiſſile Stone, clear as Water or Cryſtal of the Rock, and without Colour; enduring a red Heat without loſing its tranſparency, and in a very ſtrong Heat calcining without Fuſion."

2. (physics) Capable of sustaining a nuclear fission chain reaction.Examples: "North Korea may soon have access to regular amounts of fissile material if it doesn’t already and could be preparing Punggye-ri for a number of nuclear tests if the above analysis is correct."