A system for monitoring coring operations has a sensor 80 for detecting one or more drilling parameters relating to a down-the-hole coring operation. An indicative signal from the sensor is communicated to a signal transmitter (30) for transmitting the indicative signal to the surface. The signal transmitter is located in or adjacent the coring assembly. The signal transmitter can be a mud pulser (30) housed above a core barrel (14). Communication of the indicative signal to the signal transmitter can be wireless, hard wired or conducted through the material of an outer barrel (12) of a drilling assembly. The core barrel can include a core limit recognition/detection device (34). An adapter/sub (90) incorporates a check valve (92) to relieve excess fluid pressure if there is sufficient hydraulic lock immediately above a core sample within the core barrel as the core sample enters the core barrel.