Fluorescense, magnetism and chemical testing of minerals
Fluorescense, magnetism and chemical testing of minerals
Here are some other tests you might want to do. Some minerals are known to fluoresce or glow, others are magnetic, and some react with chemicals like acid. If you a find a mineral that shows one of these properties, you can narrow down your identification more easily.
While these tests only apply to a few minerals, doing them allows you to confirm an identification based on other properties.
Fluorescence
Fluorescence is one of the most amazing properties of minerals. If you shine an ultraviolet light on certain minerals, they appear to glow. This is called fluorescence.
Some minerals always fluoresce the same colour, while others can glow with different colours. Some common minerals like calcite and gypsum often fluoresce. Only a few minerals will always fluoresce, so this property is very useful to identify them.
Aragonite displaying pink and purple fluorescence under ultraviolet light.
It is important to remember that if you use an ultraviolet light be very careful not to shine it in anyone's eyes or on their skin, as it can be dangerous.
Magnetism
Some minerals containing iron can be magnetic. They act just like the fridge magnets you find at home. Magnetite (iron oxide) is the only common mineral that is strongly magnetic.
The simplest test for magnetism is to use a compass. A magnetic material will move the needle away from its usual position, pointing northwards.
In the image on the right, paperclips are attracted to the mineral magnetite.
Chemical testing
Simple chemical tests can be used to help us identify minerals. One of the easiest tests we can do is the acid test. When a small drop of acid is placed on most carbonate minerals they will effervesce (fizz) as carbon dioxide gas is released.
You may be able to identify some carbonate minerals like calcite by putting a small drop of an acid like vinegar or lemon juice on it. Does it fizz?
It is important to remember that acids are dangerous chemicals which can burn you. You should always have an adult to help you use any acid other than vinegar or lemon juice.
