I don’t see any evidence that boron is rare. From what I can find global consumption of boron is over 1.8 Million tons a year! Although most of that weight is in oxygen (borates), so only a faction of that weight is elemental boron. And considering how its used it seem like one of the more common elements, at least its seems much more common the uranium or thorium. I’ll affirm that Lerner’s estimates are probably within the right range and that boron fusion even at 100%+ of the worlds electricity production would not even put a significant dent in boron consumption. Making decaborane would be entirely dependent on boron, hydrogen and energy, so decaborane
