These are the heights that I know of for ore spawn heights on the Mindcrack pack. If someone could help me track down the rest of them, that would be great. Copper: 40-75 Iron: 20-40 (+0-63) Lead: 20-40 Silver: 15-35 Tin: 25-50 Diamonds: 0-16 Gold: 0-32 Ruby: 0-32 Sapphire: 0-32 Apatite: 16-88 Emerald: 4-32 Coal: 0-110 Nether: Pyrite: 0-64 This means that instead of mining on one layer, it looks like people will have to mine on three different heights at a minimum to get all ores. My suggestion would be y14, y30, and y45, at least at a quick glance. It's mainly the copper that's really annoying, though, as it's so much higher than anything else.. Of course, this all becomes mostly irrelevant when one gets a quarry going.