What is indicated by the term 'hollow cavity' in gemstone context?

The term 'hollow cavity' in the context of gemstones specifically refers to a space within the stone that is not filled with solid material, often forming as a result of internal inclusions or growth patterns during the gem's formation. These cavities can occur naturally and may be produced by trapped gas or fluid, leading to a void within the crystal structure.

Understanding hollow cavities is essential for gemologists because they can affect the clarity and overall appearance of a gemstone, and they may also influence the value. Additionally, some gemstones can develop unique characteristics or phenomena due to these cavities, such as being able to produce a specific optical effect.

While the other options touch on different aspects of gemology, they do not accurately describe the specific nature of what is indicated by 'hollow cavity.' Thus, recognizing the relationship between hollow cavities and internal inclusions is vital to properly assessing and understanding gemstones.