smelt

while true do

-- collect items
for n=8,16 do
turtle.select(n)
turtle.suck()
end

-- put items in furnace
for n=8,16 do
  turtle.select(n)
  if turtle.compareTo(1) then
   -- coal
   turtle.turnRight()
   turtle.turnRight()
   turtle.down()
   turtle.forward()
   turtle.dropUp()
   turtle.turnRight()
   turtle.turnRight()
   turtle.forward()
   turtle.up()
 elseif turtle.compareTo(2) or
   turtle.compareTo(3) or
   turtle.compareTo(4) or
   turtle.compareTo(6) or
   turtle.compareTo(7) then
   -- ore
   turtle.turnRight()
   turtle.turnRight()
   turtle.up()
   turtle.forward()
   turtle.dropDown()
   turtle.turnRight()
   turtle.turnRight()
   turtle.forward()
   turtle.down()
   turtle.drop()

 elseif turtle.compareTo(5) then
   -- gravel
   turtle.turnRight()
   turtle.drop()
   turtle.turnLeft()
 elseif turtle.getItemCount(n) > 0 then

   -- junk
   turtle.turnLeft()
   turtle.drop()
   turtle.turnRight()
 end
end

-- wait a bit
sleep(10)

-- extract ores
while true do
 turtle.turnRight()
 turtle.turnRight()
 if turtle.suck() then
  turtle.turnRight()
  turtle.drop()
  turtle.turnRight()
  sleep(5)
 else
  turtle.turnRight()
  turtle.turnRight()
  break
 end
end

end