Introducción al muestreo minero

Introducción al Muestreo
Minero
por
Marco Antonio Alfaro Sironvalle

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Preface
Is there a single important 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 clearlyis a subject of utmost importance that Dr. Marco Alfaro has decided to
bring to his audience in this simple, yet fundamental 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 justiceto the simplicity of sampling theory, and to the many services it
renders and has rendered the industry over several decades of applications.
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 allconsistent with its eminently scientific approach. Erroneous
sampling equipment and experimental procedures, incorrect application models
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 beexercised.
It is to Dr. Alfaro’s credit to have presented in a simple and short publication all the
tools that will help the professional of the 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 for this commendable effort.
Pierre Gy & Dominique Francois-Bongarcon
Sampling Associates

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

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II. Conceptos importantes en Teoría del Muestreo. Problema principal.

8III. El Muestreo Estadístico. Ecuaciones.

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IV. Consideraciones prácticas para el muestreo de minerales.

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V. Muestreo de flujos de minerales en movimiento.

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VI. Tipos especiales de muestreo minero.

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VII. El Error Fundamental del Muestreo. Teoría de Pierre Gy.

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VIII. Bibliografía.

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Anexo 1. Tabla de números aleatorios.

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Anexo 2. El ProfesorPierre Maurice Gy.

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Anexo 3. Sesgos generados por muestreo y análisis.

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Anexo 4. Ejemplos de errores de muestreo importantes.

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Anexo 5. ¿Porqué los errores aleatorios son gaussianos?

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I. Introducción e Importancia del muestreo de minerales.
Definiciones.
Según el Diccionario de la Lengua española:
Muestra es una parte ó porción extraída de un conjunto pormétodos que permiten
considerarla como representativa del mismo.
Muestreo es la acción de recoger muestras representativas de la calidad ó
condiciones medias de un todo ó la técnica empleada en esta selección ó la
selección de una pequeña parte estadísticamente determinada para inferir el valor
de una ó varias características del conjunto.
Población ó lote: es el conjunto completo deobservaciones que deseamos
estudiar.
El muestreo estadístico es diferente del muestreo de minerales:
• En el muestreo estadístico, el lote ó población está compuesto por objetos
de igual peso.
• En el muestreo de minerales, el lote está compuesto de objetos de
diferentes pesos.

Figura I.1: Muestreo estadístico y muestreo de minerales.

El muestreo de minerales. Importancia:
Casi todas las...