pos = 0

local keep = {
    "minecraft:coal",
    "minecraft:anciant_debris",
    "tconstruct:cobalt_ore"
}

while true do

    if(pos == 30) then
        turtle.turnRight()
    end

    if(turtle.getFuelLevel() == 0) then
        turtle.select(1)
        turtle.refuel()
    end

    for i=1,16 do
        turtle.select(i)
        name,exet=turtle.getItemDetail(i, false)
        notFound = true
        for _,v in pairs(keep) do
            if v == name then
                notFound = false
                break
            end
        end
        if notFound then
            turtle.drop
        end
    end

    turtle.dig()
    turtle.digUp()
    turtle.digDown()

    turtle.forward()
    if(pos == 0) then
        turtle.turnRight()
    end
    pos = pos +1
end