Spectral bludgeons' trozan sky shard frostburn property

Does the sky shard frostburn bonus stack if you dual wield the maces? Thanks.
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It does and it applies to every other one handed melee/ranged weapon.

They stack, but Grim Tools have a trouble of displaying that correctly.

And this damage is separate from the frozen core frostburn bonus?

It’s just added damage
No big secrets here