While we were all taken in by the mystery of Ralkalest, the unForgeable metal and whether or not it was the same as aluminium, there was another substance that passed under our radars: Soulstones
"Broken gods" could be referring to Splintered Shards
Soulstones are weird. They are perfect for Forgery. A soft and easy to carve chalk like substance that hardens into a quartz like substance.
Appearance-wise too it doesn't sound normal:
...but I'm no geologist, so if it is a real Earth substance like Ralkalest, just with a different name, tell me so!