Ann: Outstanding Thick Intercepts in First Step-Out Hole, page-145

Triple tubing info, assuming it's correct:

Triple Tube Core Barrels are designed to maximize core recovery in site investigation and core exploratory drilling programs.

With these Core Barrels it is possible to obtain near 100% volumetric core recovery in the most undisturbed condition possible using rotary core drilling equipment. They have been used for exploration of dam, bridge and building sites as well as the development of mineral resources.

Triple Tube Core Barrels are normally supplied with stainless steel split inner tubes. Clear plastic tubing is available in NMLC size.

The plastic tubing is used when retaining the core exactly as it is recovered from the hole is desired. The core is left in the tube and the ends are sealed.

Visual examination is possible through the tubing on site or at the laboratory. The outer tubes are hard faced at each end to reduce wear and act as a stabilizer.