local items = {
"minecraft:cobble",
"minecraft:cobblestone",
"minecraft:dirt",
"minecraft:gravel"
}

local name
local found

while true do
  for i = 1, 16, 1 do

    if turtle.getItemCount(i) > 0 then
      turtle.select(i)
      name = turtle.getItemDetail().name
      found = false
      for j = 0, #items, 1 do
        if name == items[j] then
          turtle.drop()
          found = true
          break
        end
      end
      if not found then
        turtle.dropUp()
      end
    else
      sleep(.2)
    end

  end
end