Practical Handbook of Earth Science

Jane Hodgkinson, Frank Stacey

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781351374705
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Environmental Conservation & Protection
• Index: Biological Sciences

This self-contained handbook provides a carefully researched, compact source of key earth science information and data, logically sorted by subject matter, and then cross-referenced. Appealing to both experts and non-experts alike, the book presents earth science and environmental science as closely intertwined. It includes tables of the global distributions of fossil fuels, contrasted by tables of the distribution of non-fossil energy sources. Concise explanations cover the subject matters of geology, geophysics, oceans, atmosphere with attention to environmental implications and resources.

Section VI

Rocks and Minerals

Chapter 19

Mineral Types and Characteristics

19.1 DESCRIPTIVE TERMS

Various features of minerals are used to describe and identify them. In a hand specimen, diagnostic properties, defined in the following subsections (Tables 19.1 through 19.8 and 19.11 through 19.20), are colour, streak, Mohs hardness, fracture, cleavage, habit, lustre and specific gravity.

19.1.1 Colour of Mineral in Hand Specimen

As the word implies, a hand specimen of rock or mineral is typically of a size that will fit in the hand. To be useful, it must have a freshly broken surface that exposes unweathered grains. Colour is simply a general description of light reflected from the surface, which is often different from the colour seen in unpolarised transmitted light (in thin-section under a microscope).

19.1.2 Mohs Hardness

The scale proposed in 1812 by the mineralogist Friedrich Mohs is a relative scale of scratch resistance of minerals judged by the fact that harder materials visibly scratch softer ones in hand specimens. Type specimens are used to specify the hardness scale from 1 (softest) to 10 (hardest) (Table 19.1) and common, readily available materials are generally used (Table 19.2).

TABLE 19.1 THE MOHS HARDNESS SCALE
Mohs Hardness	Index Mineral
1	Talc
2	Gypsum
3	Calcite
4	Fluorite
5	Apatite
6	Orthoclase feldspar
7	Quartz
8	Topaz
9	Corundum
10	Diamond

TABLE 19.2 COMMON ITEMS USED FOR TESTING HARDNESS
Hardness	Material
2–3	Finger nail
3	Copper coin
5–6	Knife blade
6	Broken glass
7	Steel file

19.1.3 Streak

If a mineral specimen is scratched on an unglazed porcelain plate (‘streak plate’), the colour of the resulting fine powder is its ‘streak’, which may be different from both the colours in reflected light and in ...

Table of contents

• Title Page
• Copyright Page
• Table of Contents
• Preface
• Authors
• Section I: Notation and Units
• Section II: The Building Blocks: Elements to Planets
• Section III: Global Geophysics
• Section IV: Major Subdivisions of the Earth: Structures and Properties
• Section V: Geological Activity: The Restless Earth
• Section VI: Rocks and Minerals
• Section VII: Resources
• References
• Index