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An introduction to minerals and rocks under the microscope

Introduction

Unit image

The study of the structure and characteristics of minerals is fundamental to the identification of igneous, metamorphic and sedimentary rocks, and the interpretation of the environment in which they formed. This study unit introduces the polarising microscope, the main tool used to study minerals in rock thin sections, which remains the foundation of learning to recognise, characterise and identify rocks.

The different atomic structures of minerals and their characteristics are explained, and the unit develops the skills to identify minerals using features such as mineral shape, colour, grain size, opacity, refractive index and cleavage. The unique features of the polarising microscope are also covered, including extinction, birefringence and pleochroism.

Recognising minerals and understanding their structure is the basis for recognising rocks and interpreting microtextures to learn how they were formed. Evidence gathered by careful study of minerals in thin sections is a key part of the interpretation of igneous, metamorphic and sedimentary rocks.

This unit is an adapted extract from the Open University course S276 Geology [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .

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