I don't pretend to know in this case, but sometimes you can tell by the lattice, see https://en.m.wikipedia.org/wiki/Widmanst%C3%A4tten_pattern https://en.m.wik

I don't pretend to know in this case, but sometimes you can tell by the lattice, see https://en.m.wikipedia.org/wiki/Widmanst%C3%A4tten_pattern https://en.m.wikipedia.org/wiki/Widmanst%C3%A4tten_pattern The only way a widmanst pattern forms is by slow cooling of the iron over millions of years. Check out the wiki section on why it can't be reproduced in a lab