3.8: Electrical Properties

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3.82.jpg — 3.82 Native copper from Pima County, Arizona

Electricity can be conducted if a mineral contains electrons that can move throughout its structure. (See the discussion of diamond and graphite in Box 3-3.) So, minerals with metallic, or partially metallic bonds – like many sulfides — are good conductors. The native metals, such as copper, are the best examples. This photo (Figure 3.82) shows a “branch” of native copper with several small quartz crystals on it. The branch was extracted from a rock matrix. Sulfide minerals, because they commonly have partially metallic bonds, are also good conductors.

Small amounts of electrical conduction may also occur in minerals with defects or other imperfections in their structures. And, some minerals, while being unable to conduct electricity, may hold static charges for brief times. They may be charged by exposure to a strong electric field, a change in temperature, or an application of pressure. A mineral charged by temperature change is pyroelectric; a mineral charged by pressure change is piezoelectric. Because they are difficult to measure, however, electrical properties are not often used for mineral identification.