1. Identifying Minerals

2. Crystal Form
Some minerals can form distinctive crystalline shapes that make them very recognizable. Ex: Halite (cubic), Quartz (Six-sided and pointed).
Not all minerals will form perfect crystals and so identification based only on crystal form is rare.

3. Luster
The way that a mineral reflects light from its surface is called luster.
Two types: Metallic and Non-metallic luster.
Metallic: silver, gold, copper
Non-Metallic: They do not shine like metals. Instead, they could be described as dull, pearly, waxy.
Rather subjective and so luster should be used in conjunction with another process.

4. Hardness A very useful and reliable test for identifying minerals.
Hardness is a measure of how easily a mineral can be scratched.
The German geologist Friedrich Mohs developed a scale by which an unknown mineral’s hardness can be compared to the known hardness of ten minerals.

5. Cleavage & Fracture
The arrangement of atoms within a crystal will determine how a mineral will break. Minerals break along planes where atomic bonding is weak.
A mineral that splits relatively easily and evenly along one or more flat planes is said to have cleavage. (ex: Mica and Halite)
Minerals that break with rough or jagged edges are said to have fracture. Ex: Flint (conchoidal fracture)

6. Cleavage & Fracture

7. Streak
Streak is the colour of the mineral when it is broken up and powdered. This can usually be seen by running a mineral across an unglazed porcelain plate.
Non-metallic minerals – usually white
Metallic minerals – varies (most useful for metallic minerals)
Can you use streak to identify all minerals? Why or why not?

8. Colour
A very noticeable feature of a mineral and yet one of the least useful.
Colour is often the result of trace elements within the mineral.
Ex: Quartz (Amethyst, Rose Quartz, Red Jasper, Citrine)

9. Density and Specific Gravity
Density = mass/volume
Density does not depend on the size and shape of a mineral. It only depends on the internal atomic structure. For this reason, it is a useful identification tool.
If the sample is too small, it is difficult to determine the density by conventional means. Therefore, geologists typically measure density by determining a materials specific gravity.
Specific gravity – ratio of the mass of a substance to the mass of an equal volume of water at 4 degrees Celsius.

10. Texture How does a mineral feel to the touch?
Similar to luster, this is a subjective measurement.
Ex: Talc is greasy and Fluorite is smooth.

11. Special Properties Double Refraction – Iceland Spar (Calcite)
Effervescence – Calcite will fizz when exposed to an acid (release of carbon dioxide)
Magnetism – Magnetite (iron containing minerals)
Iridescence – Labradorite (caused by the bending of light rays)
Fluorescence – Fluorite, Calcite (glows in the dark when exposed to UV light)