Shearing Faint Amaranth drops glowstone in addition to the plant itself, so it's possible to infinitely create glowstone at a cost of nothing but the durability of the shears you use.

Using astralsorcery-1.12.2-1.8.4 for MC 1.12.2 and forge 2566

What other mods?

This is not vanilla behavior. definintely mod interaction.

@666lumberjack update please.