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Comparison of Precision in Assay Values

Brooke Miller
Thursday, November 30, 2017
First presented: 
LinkedIn Published Article
Gold is scarce in nature. Even in gold deposits with economically viable grades, the abundance of gold is a small quantity compared to the rock mass. Mineral resource estimates are based on analytical data from drillhole samples, called assays. The units of the assay data and the precision of the values impact the resource estimation in several ways. In this article, we will illustrate these impacts, starting with the inherent difference in the precision of units. In most of the world, the metric system is prevalent, and there is no question about the units to use for resource estimation: grams per metric ton, equivalent to parts per million. However, in the United States, mines are planned and built in length and weight units derived from the Imperial system. To add to the unit complexity, the troy ounce is the common weight unit for precious metals, and is slightly heavier than the avoirdupois (avdp) ounce, which is the common definition of “ounce” in the U.S. (i.e. one pound is 16 avdp ounces).

Original Article on LinkedIn

Feature Author

Brooke Miller Clarkson
Brooke Clarksonn is a resource geologist with over eleven years of experience in exploration and mining projects in the western United States. She is a Qualified Persons (“QP”) according to CIM NI 43-101 requirements. Her primary expertise is in geological modeling and data analysis, and she has contributed to technical reports from resource to feasibility stage. Field experience includes drill core and chip logging, highwall and drift mapping, and drilling program management. Software proficiency includes Leapfrog 3D®, MineSight 3D®, and familiarity in a variety of related programs.
Geological Modeling and Data Analysis Expert
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