What is electrical conductivity?

• A. A measure of how well an electrical current passes through a material.
• B. A measure of the color of a gemstone.
• C. A method to determine refractive index.
• D. A test of hardness.

Answer: (A)

Electrical conductivity is a measure of how well an electrical current can pass through a material. It depends on the availability and mobility of charge carriers; metals with many free electrons conduct electricity readily, while materials like diamond have very few free charge carriers and act as poor conductors. In gem testing, this property is useful because diamonds are typically poor conductors at room temperature, whereas some other gemstones (like silicon carbide, used in moissanite) can conduct electricity under test conditions. The other options describe color, refractive index, or hardness, which are unrelated to how easily electricity moves through a material.