In response from a request for a system that could be used to collect all the gas held within rock using mineral type drilling systems. Sigra has designed a modification of the Boart Longyear HQ-3 core barrel. This is designed to collect all the gas released during coring or the retrieval of the wireline inner tube to surface with the core. Residual gas may then be obtained from the core so that the total gas content is measured, without resort to estimates for loss.