Quality Assurance / Quality Control (QA / QC)
The Quality Assurance / Quality Control (QA/QC), as its name implies, is a system of operational processes to ensure the integrity of the information. The QA/QC procedures allow for verification and optimization of the sampling data. As part of the QA/QC process, the following control samples are inserted: blank, standard, and field duplicate. Each set of 20 samples contains 1 blank, 1 standard, and 1 duplicate sample as well as the 17 drill core samples.
Blanks are made from unmineralized, homogenous material. At the San Acacio project, blanks are typically made from crushed building limestone acquired from a local hardware store. Blanks are inserted at a rate of one blank within every 20 samples. Blanks may be inserted randomly within the sequence of 20 samples, guided by the discretion of the logging geologist. It is preferable to occasionally insert blank material after well-mineralized zones in order to determine if there are any concerns with the laboratory techniques (for example, cross-sample contamination resulting from the previous higher-grade sample). The entire insertion of blanks process is intended to yield an overall blank insertion rate of approximately 5% of the total sample population.
Standard material at the San Acacio project consists of accredited reference materials and certified reference materials (CRMs), the latter are preferable. Standard material is selected to verify the grades of targeted elements and must be certified for all economic elements to be reported in the mineral resource. Standards are selected to validate the full range of metal grades, including low, average, and high grades with additional rigor at or near the resource cut-off grade when possible. The previous resource estimate cut-off grade for the San Acacio project was 100 g/t Ag Eq with average resource grade of 182 g/t Ag (Technical Report and Resource Estimate, San Acacio Silver Deposit, Zacatecas Sate, Mexico, by Giroux and Cuttle; September 2014). Base metals, including Pb and Zn, will be incorporated into any future resource estimates. Currently Defiance Silver Corp. uses five different CRMs supplied by OREAS with analytical ranges of 0.204 g/t – 2.29 g/t Au, 19 g/t – 1015 g/t Ag, 119 ppm – 4114 ppm Pb, 404 ppm – 11121 ppm Zn and 499 ppm – 50300 ppm Cu.
Standards are inserted at a frequency of one within every 20 samples. The logging geologist will select the most appropriate standard for the batch of 20 samples, taking into account the potential grade and metal suite of the samples according to his/her observations. High-grade standards are most appropriate where high-grade values are expected, low-grade standards where low-grade values are expected, etc. Particular care is given to select the appropriate standard grade with respect to the tenor of different metals anticipated from observed mineral assemblages.
Two types of duplicate samples are employed at the San Acacio project: field duplicates and pulp duplicates. A field duplicate replicates the entire sampling process and thus captures all levels of potential error. A pulp duplicate will contain the same sampling and lab preparatory errors, but if submitted to different labs and/or at different times, this will capture the different laboratory digest and analytical errors. Submission of field duplicate samples to the routine lab will be used to assess error and bias in sampling and laboratory processes. Submission of pulp duplicates to alternative labs is used to assess error and bias between laboratories.
Field duplicates are inserted at a frequency of one within every 20 samples. Field duplicates of diamond drill core will be comprised of half of the primary sample, such that both the primary sample of which the duplicate is being taken, and the duplicate itself, consist of quarter core.
Sample preparation is performed at the Zacatecas, Mexico, ALS Chemex preparation facility. Samples are analyzed by ALS Chemex Laboratories in Vancouver, Canada. All elements except Au and Hg were analyzed by a multi-element geochemistry method utilizing a four-acid digestion, followed by ICP-MS detection [ME-MS61m]. Mercury was analyzed after a separate aqua regia digest by ICP-MS. Overlimit assays for Ag, Pb, and Zn were conducted using the OG62 method (multi-acid digest with ICP-AES/AAS finish). Gold was measured by fire-assay with an ICP-AES finish [50 g sample, Au-ICP22].