Stahlman's ooze

Stahlman's Ooze was an (initially) unnamed substance which oozed as a byproduct of the drilling conducted by Professor Stahlman. It was a green, viscous substance which originated under the Earth's crust, and when touched by humans it altered them in both a physical and psychological manner, making them crave the heat and altering their biology, turning them almost rabid. These humans were called Primords. (DW: Inferno)

This ooze was part of the "immune system" for the Earth, which "activated" when the Earth was "deeply disturbed". Incidents of this "disturbance" included, but were not limited to, the explosion of Krakatoa and the above mining incident.

The Glasshouse was later known to have held a sample of the ooze for study. (MA: Who Killed Kennedy) It was also used to transform a Doberman into a creature know as the Stalker. (MA: The Scales of Injustice)

There is a possibility that this ooze is infact connected to the Xylok or even the Racnoss, as both beings exist deep inside the Earth. That Torchwood would later manage to drill right to the Earth's core, seemingly without obstruction, raises many inconsistencies. This, plus the apparent 'auto-defense system' nature of the ooze, could indeed link it to one of the several extraterrestrial objects lodged within the Earth's interior.