This is one of the easiest ways of identifying minerals and it is usually the first test applied to them. Some minerals, however, change color when they come in contact with other elements: silver, for example, tarnishes when it is exposed to air. Others, like quartz and tourmaline, can take on a wide range of colours. Their are also finer details to this way of identifying :
- cannot be seen through
allows light to pass through it and objects on the other side can be seen.
light passes through it, but objects on the other side cannot be seen clearly.
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