Deep Slate/Grimstone ores take 2x longer to smelt/produce more?

As an addition to "new mining strategies", perhaps have the tougher rock's ores also take longer to smelt? (As they currently also take longer to mine!)

Perhaps because of the increased time, maybe they could have a chance of producing double the amount? (Which may need to be something new programmed into the game because it's furnaces, not fortune)

The blast furnace also currently cooks regular ores 2x faster, so the idea is to have blast furnaces cook them at normal speed! And it would provide incentive to putting more resources into them, to smelt more later when transitioning to deeper mining!

I partially feel that 2x may be too long however, as currently the stones take only a tiny bit longer to mine, so it'd be something to play with! Maybe something closer to 1.5 or 1.2x longer?

Then if it ends up being 1.2x slower, maybe a 20% chance to produce double drops? (Blast furnaces reducing it to 0.8x time, with an increased 25-30% chance double drop perhaps?)