PROPERTIES

Minerals can be identified visually by building up evidence from all their properties. We will use the following:

Lustre

Colour

Habit

Hardness

Streak

Cleavage

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Lustre

Lustre refers to the way in which the mineral reflects light. It may be referred to as metallic (like a metal) or non-metallic. Metallic & non-metallic are the most frequently lustres used but non-metallic lustres are sometimes subdivided.

Colour:

This is the easiest property to see and not always the most useful.

It is important to describe the colour of a freshly broken or scratched surface.

Hardness:

The hardness of a mineral is determined by what it will scratch and what scratches it. In 1822, the Austrian mineralogist devised a scale from 1 - 10 using 10 common minerals:

We do not always have this set of minerals but the following are usually readily available:

or Key to Mineral ID

Streak:

Streak is closely related to colour. However, in many instances, the colour of the mineral when it is crushed into a powder is different to the lump. If the mineral is scraped across some unglazed porcelain, it leaves a trail of powder if it is soft enough. The colour of this powder is called the streak of the mineral.

Cleavage:

Cleavage describes how a mineral may split easily in certain directions and not in others. For example, Galena splits in 3 directions at right angles which results in the formation of cubes of the mineral. Cleavage is mostly used to confirm certain minerals.

PROPERTIES

Minerals can be identified visually by building up evidence from all their properties. We will use the following:

Back to Main Page

Lustre

Lustre refers to the way in which the mineral reflects light. It may be referred to as metallic (like a metal) or non-metallic. Metallic & non-metallic are the most frequently lustres used but non-metallic lustres are sometimes subdivided.

Vitreous

The lustre of glass

Adamantine

The lustre of a diamond

Waxy

With a wax like appearance

Colour:

This is the easiest property to see and not always the most useful.

It is important to describe the colour of a freshly broken or scratched surface.

Hardness:

The hardness of a mineral is determined by what it will scratch and what scratches it. In 1822, the Austrian mineralogist devised a scale from 1 - 10 using 10 common minerals:

1 - Talc

6 - Orthoclase

2 - Gypsum

7 - Quartz

3 - Calcite

8 - Topaz

4 - Fluorite

9 - Corundum

5 - Apatite

10 - Diamond

We do not always have this set of minerals but the following are usually readily available:

2.5

Finger Nail

3.5

Copper Coin

5.5

Pocket Knife

>6

Scratches glass

or Key to Mineral ID

Streak:

Cleavage:

Cleavage describes how a mineral may split easily in certain directions and not in others. For example, Galena splits in 3 directions at right angles which results in the formation of cubes of the mineral. Cleavage is mostly used to confirm certain minerals.