I've mined at the higher level one, its not for ores, its for jewels.
Both the mines have separate items.
Forest Coal Mine is for Ores, Crystal Coal Mine is for Jewels.
You can get fair ore and copper at the crystal coal mine, however this means you've done really bad in mining, stick to the forest coal mine for your ores, its pretty much pointless to move ahead to the crystal coal mine for ore.
And ore drops are respective of your level and skill.