What causes thermal shock in gemstones?

Thermal shock in gemstones occurs due to sudden, extreme temperature changes. When a gemstone experiences rapid heating or cooling, different parts of the stone can expand or contract at different rates. This inconsistency in thermal expansion or contraction leads to internal stress within the gemstone. If the stress exceeds the material's ability to withstand it, this can result in cracks or fractures within the stone.

This phenomenon is particularly significant in gemstones with lower thermal conductivity, as they are less able to evenly distribute the heat throughout their structure. It is essential for gem cutters and jewelers to handle gemstones with care, particularly when exposing them to sources of heat or cold, to prevent thermal shock and the subsequent damage it can cause.

The other options relate to different types of stress or environmental effects but do not directly address the specific cause of thermal shock. For instance, prolonged exposure to light can lead to fading or changes in color, mechanical stress during cutting can cause brittle stones to fracture, and chemical reactions may result in surface degradation. However, none of these processes involve the rapid temperature fluctuation that characterizes thermal shock.