Other Properties

Some minerals have unusual properties. For example, acids dissolve calcite easily. If you put a few drops of dilute hydrochloric acid on calcite, the calcite will bubble vigorously. In this way, calcite can be distinguished from the similar-looking mineral quartz. Another mineral with an unusual property is magnetite, which is strongly attracted by a magnet. Fluorescent minerals like fluorite give off visible light when they are held under an ultraviolet light. Certain minerals produce small flashes of light when rubbed with a metal point. For example, a form of quartz called rock crystal emits these flashes when it is sawed.

Some minerals have unusual electrical properties. Quartz and tourmaline, for example, become electrically charged when heated and cooled or subjected to pressure. Quartz's electrical properties have applications in electronics equipment.

Iceland spar is a transparent form of the mineral calcite that has the property of refracting light into two separate rays. If you looked at these words through a piece of Iceland spar, you would see a double image of the words. This property is useful in certain optical instruments.