Or now:
Pigman spawner: Gold
Minium shard: Gold->Iron
Tome Of Alkahest: 1 stack of gold to-> half a stack of lapis BLOCKS
Works, but not as fast as the other way. You are dependent on the nugget drop rate of the pigman. On a server over time you will have more then you can spend anyway.
You still have to put an other fabricator putting nuggets into ingots.
To make sure there is always a minium stone in the fabricator you could set up a mob farm and use a fabricator to make stones.
I´m not familiar with BC gates, but there should be a way to just refill the minium stone to the fabricator when its used.
[edit] Ok the minium thing is already solved :O