OreGrow is a Bukkit plugin that is to allow players to grow ores using furnaces and fuel

How to use:
Place furnace
Place single redstone wire adjacent to furnace
Place SOLID BLOCK of iron, gold, or diamond adjacent to the redstone with, such that all three (furnace, restone, solid block) are all in a DIRECT LINE.
These three blocks must be Co-Linear.
To obtain Coal or charcoal, place 4 coal/charcoal in crafting grid and craft Coal ore blocks.
Smelt coal ore blocks in Furnace apparatus created in previous steps to grow ore.

Iron ore requires the smelting of 1 coal ore
Gold requires 2
Diamond requires 4

Please note the following limitation: If you create a diamond apparatus, and
smelt 7 coal ore, then remove the 7 newly-created cobblestone before the 8th
is smelted, diamond ore will not be grown.  Growing occurs when a multiple of
the required number has just been achieved in the output of the furnace.
This also applies to Gold and Iron as well.