Sample Preparation and Quality Control Measures. RC Rotary Drilling For each drill hole requiring reverse circulation drilling, the drill crew was provided with a set of bags prenumbered in sequential order (1 through XXX). The bags themselves carried only an exterior designation of drill-hole number and sample number. Since the sample numbering sequence includes blanks and standards inserted every 10th sample, the driller's sampler cannot be expected to keep track of his sample collection based on the bag numbering. (Conventionally, RC exploration either relies on direct footage, or sample numbers in multiples of 5 feet). In order to prevent numeric confusion, yet permit Atna to submit "blind" sample numbers to the assay lab, several steps were taken. First, the rig sampler was provided with chip trays accurately numbered with both true footage and the corresponding bag number. Second, he was provided with a deliberately incomplete set of bags; he was deprived of all the bags intended for standards and blanks. Third, since the ultimate completed depth of the hole is not known in advance, the bags for duplicates (to be collected every 100') were merely prelabeled with the letters 'A,' 'B,' 'C,' etc and flagged with a tear-off paper tag. The cuttings and tray chips themselves were collected as a continuous fraction of the return stream from the drill rig. The cuttings were diverted to a 10"x17" mesh bag, and the tray chips were diverted to a kitchen strainer. The filled chip trays were collected by an Atna geologist for logging under a binocular microscope and remain with Atna, while the sample bags are shipped to the analytical laboratory for preparation and assay. Sample bags are allowed to dry/drain at the drill site and an Atna geologist visits the drill site and confirms the numbering and accuracy of the sample suite. Samples are then brought down to the shipment staging area, Atna personnel then relabeled the 'A,' 'B,' 'C,' etc. bags (representing the 100' duplicate samples) by assigning the correct sequential numbers for them; they form the tail-end of the sample list submitted to the lab and therefore are blind to the laboratory personnel. The samples are then loaded in 4' x 4' x 3' wooden crates for pickup by the laboratory.
Sample Preparation and Quality Control Measures. Core Drilling Traditionally, core is forced out of core tubes by upending the tube, and tapping on it with a ball-peen hammer. Exceptionally, to preserve structural integrity, companies have requested/required that drillers attach a water line to the cap of the core tube and gradually "pump" the core out. This method is often ignored by the drill crew in the absence of close supervision. The triple tube core barrel eliminates this problem by allowing the interior core container to be opened lengthwise. Atna used a triple-tube for all of its shorter holes completed by Rxxx Drilling. The core so obtained was carefully pumped out of the tube assemblies and laid out on a rack, intact. The drill crew recorded the Rock Quality Data (RQD) values on a worksheet and photographed it, using a digital camera to capture both the core and a whiteboard showing hole number and footage interval on display. For the deeper holes that did not receive triple-tube treatment and were therefore emptied in the traditional way, the geologist later recorded the most credible RQD values from core in the core box, and did not photograph it for RQD purposes, since it has already been 'broken up' for boxing. The RQD measurement was established by measuring the total length of all pieces in a core run that exceed 2x the diameter of the core. In practice, 2x the core diameter is 0.3 feet. This number was summed, and written as a numerator in a fraction where the denominator was the total run drilled. On worksheets maintained by Axxx, the raw values recorded are the length of the longest piece, and the sum of all qualifying pieces within the run Dividing the former by the latter yields the numeric RQD. The drill crews placed the core in waxed cardboard core boxes, with tops and bottoms accurately labeled as to Company - Property- Hole ID - Box # -- From - To. The bottom of the core box was laid out longways from left to right, with the marked or labeled end to the left and the unlabeled end to the right. There are 5 rows or trays. The first portion of core was laid in the upper left-hand tray, and continuously laid in the tray from left to right, advancing "down" one row as each tray is completed. The bottom of the core terminated in the lower right corner. A wooden block was inserted at the end of each run, and in locations deemed important by the drillers to note adverse conditions, such as caving, voids, or mislatches (situations where the core tube failed to seat properly in the core b...
