Core

The core is a cylindrical rock sample taken from the formation for geological analysis. (in drilling)
In order to retrieve the core as intact as possible, it is cut from the rock by an annular core bit. The central column of rock passes through the centre of the bit and, as the bit cuts deeper, is received by a hollow cylindrical core barrel above the bit, where it is retained and protected by a series of rubber baffles. When the bit has cut deep enough to fill the core barrel, it is withdrawn from the hole and the core extracted. In this way the actual sequence of rock strata is preserved.