This is highly variable, and depends upon the richness of the ore. For example, the mines of Michigan's Keweenaw Peninsula mined primarily native copper, occasionally found in immense, multi-ton masses, which were actually quite a nuisance as explosives had no effect upon them and they had to be chiselled into managable sizes using hand tools. So in that case, to get a pound of copper, you'd smelt about a pound of ore. In mines with low grade ore, eg. Arizona, it will take a lot of rock to produce a pound of copper... but every mine is different.
Copper, to make Bronze.
Using your smelt skill you get from purchasing mining you smelt the Copper Ore you get into bars at a ratio of 1:1
To make bronze, smelt tin ore and copper ore.
smelt
smelt
The largest source of copper is from porphyry ore.
here is how you make no-member bars up to gold: To make Bronze bars, smelt copper and tin ores together. To make Blurite bars, smelt a blurite ore. To make Iron bars, smelt an iron ore. (50% chance of success) To make Silver bars, smelt a silver ore. To make Steel bars, smelt two 2 coal ores and one iron ore together. To make Gold bars, smelt a gold ore. To get a 100% success rate with iron smelting purchase a ring of forging from the grand exchange, northern Varrock. This saves a lot of time and effort and quickly pays for itself.
Runescape
You take the metal ores - in the case of bronze, you need 1 copper + 1 tin for every bronze bar - to a furnace. Alternately, you can use the "Superheat Item" magic spell. This requires Magic level 43, and costs a Nature Rune each. Because of the cost of the Nature Rune, it isn't worth-while for most low-level players.
a copper ore
Copper ore is called CHALCOPYRITE.
You take 1 Iron Ore and 2 Coal and put it in the Furnace.