We're currently not generating a recipe for gold dust (and possibly iron dust/mod-specific dusts, haven't tested) to be smelted/blasted into ingots.
At first glance this seems to be a non-issue, as we don't add a way to obtain gold dust in this mod yet.
Some mods (like Futurepack) default to other mods' dusts by default, however, as seen here in the Mystic Mods discord.
In this case, we want to generate a smelting recipe, potentially for all of the dusts, even if they're not "enabled."

Mystic Mods Versions

• MysticalLib: 1.16.1
• MysticalWorld: 1.9.3

Other Versions:

• Forge: 28.2.11
• Minecraft: 1.14.4

That's really strang ebecause I swear I actually fixed this.l.. I'll take another look into it.

Same for Iron dust.

And pretty much every other metal

Well, this certainly isn't the case for the latest release of Mystical World -- iron and gold dusts were missed, but I'm looking in the generated resources folder and I see "copper_ingot_from_smelting_dust", etc.

Iron and gold were missed purely because the block <-> ingot <-> nugget recipes were abstracted out and I moved the dust into those, and as we don't control iron blocks or nuggets, etc, they somehow got lost in the conversion to Registrate.