For reference:
28 There is a mine for silver
and a place where gold is refined.
2 Iron is taken from the earth,
and copper is smelted from ore.
3 Mortals put an end to the darkness;
they search out the farthest recesses
for ore in the blackest darkness.
4 Far from human dwellings they cut a shaft,
in places untouched by human feet;
far from other people they dangle and sway.
5 The earth, from which food comes,
is transformed below as by fire;
6 lapis lazuli comes from its rocks,
and its dust contains nuggets of gold.
7 No bird of prey knows that hidden path,
no falcon’s eye has seen it.
8 Proud beasts do not set foot on it,
and no lion prowls there.
9 People assault the flinty rock with their hands
and lay bare the roots of the mountains.
10 They tunnel through the rock;
their eyes see all its treasures.
11 They search[a] the sources of the rivers
and bring hidden things to light.
Shaft mining may appear intimidating, and certainly gets difficult, but it's a fairly natural thing to do. By far the hardest part of mining is getting rid of all the rock you don't want, and so following a vein as directly as possible is highly encouraged--especially when you're doing it all by hand with a pick and buckets.
Mining is indisputably old. Neolithic flint mines with shafts and galleries have been found as early as 4300 BCE or so, dug by hand with antlers. Later widespread use of bronze would make mining big business, especially of the relatively rare tin. Iron is more common, but also would be followed underground in the right circumstances.
The Book of Job isn't securely dated, but it's probably 6th century BCE, give or take a few hundred years, and is thus fairly young in relation to mining, falling, as it obviously does, in the Iron Age.