The hypothesis is that they are shards of an ancient meteore fall on Atmora long ago , those shards scattered all around the sea of ghosts and in Solstheim was used for the weapons and holy stuff...
Can it make sense?
I have read also that ancient nords might have used it for crafting weapon , so I tought also of a rawer more ancient form that could be used to make weapons to have a sort of dualism like in skyrim for the steel and skysteel of the draugr weapons, so could be draugr stalhrim and the modern one.