To be more clear, you need shovels, TNT, and dynamite to mine. shovels give you 4 random ores, 3 for TNT, and 2 for dynamite. It takes 3 like ores to make one bar. 8 hrs for silver, 12 hours for gold and 16 hours for platinum. you need 4-5 assorted bars to make one jewelry item. and rings need an actual diamond!
You can see why you need five smelters, and a constant supply of mining material to make your jewelry machine worth it. And the 1st smelter you buy is cheap, but it goes up in price, I think the last one was 60k or so.
I say get your other machines first, and then open the mine and buy smelters
GC: andreangentry Lvl 55