Muestreo

Introducción al Muestreo Minero
por Marco Antonio Alfaro Sironvalle

Santiago, Chile, 2002

Instituto de Ingenieros de Minas de Chile.
Encomenderos 260, Of. 31. Tel (56-2) 2461615, Fax 2466387. E-Mail: instituto@iimch.cl Web: http://www.iimch.cl Santiago, Chile, 2002.

Es Propiedad. Prohibida la reproducción parcial o total sin autorización del autor.

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Preface Is there a singleimportant decision made on a mining project that is not in a way or another, directly or indirectly based on some kind of assayed grade, or in other terms on a mineral sample? And who, in the end, is responsible for the devastating consequences of taking bad samples? It clearly is a subject of utmost importance that Dr. Marco Alfaro has decided to bring to his audience in this simple, yetfundamental leaflet, which is directed not only to technical professionals of the mining industry, but also to those who manage them and bear the ultimate responsibility for the results and consequences of mineral sampling. In this piece of work, Dr. Alfaro genuinely makes justice to the simplicity of sampling theory, and to the many services it renders and has rendered the industry over several decades ofapplications. Like in many a discipline, however, there is Sampling and ‘Sampling’, good and poor applications, enlightenment and ignorance, science and witchcraft. Practical implementations have kept improving, but have also suffered through many avatars, not all consistent with its eminently scientific approach. Erroneous sampling equipment and experimental procedures, incorrect applicationmodels and formulae, based on a highly commercial but appallingly arbitrary modus operandi, have made their way into our service and equipment markets, and are currently offered to the non-discerning professional. The utmost critical sense and prudence must be exercised. It is to Dr. Alfaro’s credit to have presented in a simple and short publication all the tools that will help the professional ofthe industry, as well as the managers and directors who are committed to the success of mining projects, tell the good from the bad, and not fall prey to ‘imitation sampling theory’ which plagues our plants, our mines, and even some of our ‘consultants’ calculations. As active devotees to the future and growth of genuine sampling theory, we feel indebted to Dr. Alfaro and thank him very much forthis commendable effort. Pierre Gy & Dominique Francois-Bongarcon Sampling Associates

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Prólogo Estimado lector, he decidido publicar en el lenguaje más simple posible una introducción a la Teoría del Muestreo Minero, para ello, basado en mi experiencia docente, he considerado fundamental incluir el máximo de gráficos. En algunas ocasiones el material presentado corresponde a minas conocidas,he omitido sus nombres, por razones de discreción minera. Agradezco sinceramente la ayuda, consejos y apoyo de los Doctores Pierre Gy y Dominique Francois-Bongarcon. Agradezco también a Ana María por su apoyo y consejos. Estimado lector, agradeceré contactarme ante cualquier duda, comentario o sugerencia. Juntos mejoraremos futuras ediciones del libro.

Marco Antonio Alfaro Enero, 2002.

AAna María, Marco y Sebastián.

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TEMARIO. I. Introducción e Importancia del muestreo de minerales. II. Conceptos importantes en Teoría del Muestreo. Problema principal. III. El Muestreo Estadístico. Ecuaciones. IV. Consideraciones prácticas para el muestreo de minerales. V. Muestreo de flujos de minerales en movimiento. VI. Tipos especiales de muestreo minero. VII. El Error Fundamental delMuestreo. Teoría de Pierre Gy. VIII. Bibliografía. Anexo 1. Tabla de números aleatorios. Anexo 2. El Profesor Pierre Maurice Gy. Anexo 3. Sesgos generados por muestreo y análisis. Anexo 4. Ejemplos de errores de muestreo importantes. Anexo 5. ¿Porqué los errores aleatorios son gaussianos? 5 8 14 18 40 49 64 74 75 76 77 78 79

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I. Introducción e Importancia del muestreo de minerales....