Abstract: A sturdy tubular “sub” apparatus for collecting geological samples (Geological Sample-Sub or GSS) that may be entrained within a conventional drill string apparatus for conducting a drill-stem-test. The apparatus may be manufactured from conventional drill-collar stock and may be provided threads at each end of a standardized thread size so that it may be readily exchanged with or attached to other subs comprising the drill string apparatus. The drill string apparatus with the incorporated GSS may be lowered in a closed and empty state into a drilled hole whereupon it is packed off and the apparatus may be opened. A slit-like opening in the GSS permits entry of rock samples into the tubular apparatus, whereas baffles located within the apparatus near both ends prevent the escape of the samples as fluid in the hole rushes through the open drill string assembly.