Apologies, I was thinking more of Ethan Siegel's blog post about it all where he attempts to discredit Prof. Loeb by referring back to one of his own blog posts where he posits that there is every possibility that IM1 might have been a piece of technology and it would be pretty incredible if it turned out to be. The gist of them all was to keep an open mind about all possibilities.

Prof. Gallardo is correct in his hypothesis that there is the possibility that some of the spherules could indeed be fly ash but I feel overreaches in his conclusion that a similar composition negates the meteoric origin theory. We cannot draw any straight conclusion from 5 spherules out of 700. Fly ash normally also contains only 5ppm of Be, much lower than the 20ppm of Prof. Loeb's samples.

I work with fly ash as a concrete additive in my lab. It has very similar physical characteristics as natural pozzolanic ash which whilst not as common, can contain naturally occurring Be. Is it not possible that a meteorite that falls to earth could be debris from a planet that was once volcanically active?