There are several electrical properties of minerals that are sometimes useful in identification, and there are others that are simply interesting but not of much value for identification.
- Electrical Conductivity (or it's compliment, resistance)
- Most minerals are electrical insulators (104+ ohm-meters). A few, mostly metals plus graphite, are conductors.
Note that most elements are metals and excellent conductors of electricity, with
resistance in the range of 10-8 ohm-meters. And a few elements are semi-conductors, such as silicon, germanium,
and tellurium. Measurement of electrical resistance can distinguish between
conductors, as long as the element is relatively pure and the sample is
relatively large, although the metals have sufficiently high conductivity that,
for small samples, they'll have close to zero resistance (values of 10-8
ohm-meters are typical). Graphite has a measurable resistance (10-5
ohm-meters), and is easily distinguished in this way from molybdenum whose
crystals are similar but which is a conductor. Semi-conductors can be identified
based upon measurements of their band gap voltage, or via their resistance once
that voltage is exceeded (silicon is 10, germanium is 10, tellurium is ).
- Electrostatic generators
- A few minerals, such as sulfur, are such good insulators (1015
ohm-meters) they can easily generate static electricity.
- Some minerals, including tourmaline and galena, generate electric fields when squeezed (or conversely they change dimensions when an electric field is applied).
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