Difference in furnaces?

[BoaConstrictor]

And this is also valuable, and should be still up to date for the current live version.

A coal miner's guide - Spark and furnace values included

Hi everyone, while playing the game I’m finding plenty of higher metals I want to smelt and process, but it turns out more fuel is always needed for smelting metals and converting into spark for processing. I wasn’t entirely satisfied with the existing thread about spark values for fuels and I wanted to answer for myself two questions: Are some fuels more efficient to use in the furnace than in Spark cores? Which coal type should I hunt for when I urgently need spark? It was time for science…