I've just been experimenting with skulls and bones in reactions, and so far it looks like they work as long as you specify a creature.
[REACTION:GOBLIN_TROPHY_MAKING]
[NAME:make goblin trophy material]
[SMELTER]
[REAGENT:5:BONES:NO_SUBTYPE:BONE:GOBLIN]
[REAGENT:5:SKULL:NO_SUBTYPE:GOBLIN:NO_MATGLOSS]
[PRODUCT:100:3:STONE:NO_SUBTYPE:STONE:GOBLIN_TROPHY_STONE]
This building material is suitable for beds, tables, doors, walls, and flooring. It's like they come pre-engraved!
[REACTION:TITANIUM_MAKING]
[NAME:make titanium bars]
[SMELTER]
[REAGENT:1:BAR:NO_SUBTYPE:BAR:TITANIUM_ROUGH]
[REAGENT:10:PLANT:NO_SUBTYPE:ROCK_SALT_CRYSTAL_PURE:NO_MATGLOSS]
[REAGENT:10:BAR:NO_SUBTYPE:COAL:CHARCOAL]
[REAGENT:5:BONES:NO_SUBTYPE:BONE:ELF]
[REAGENT:5:SKULL:NO_SUBTYPE:ELF:NO_MATGLOSS]
[PRODUCT:100:1:BAR:NO_SUBTYPE:METAL:TITANIUM]
[PRODUCT:100:3:BAR:NO_SUBTYPE:METAL:SLAG]
[FUEL]
Titanium, the strongest natural material available. Due to our technology, vacuum chambers are just outside reach, meaning that the Kroll process cannot be obtained. The Hunter process can be roughly emulated with large amounts of high-quality salt crystals for Chlorine and charcoal for Coke (I hate Coal). At this point sodium would be used to form pure Titanium, but the purest source is Cryolite, which is horribly rare. Instead, the skeletons of elves is used.
For best results, the elves should be placed in a clear glass room underground, away from the sun, watching farmers harvesting various mushrooms while a covered magma vent gently cooks them. Once properly marinated, seal the room and fill with water. Wait until the cave-worms have left only the bones, then hurl the remains into the Titanium smelter while explaining to their liaison the benefits of progress.