What are the needles of actinolite found in emerald classified as?

The needles of actinolite found in emerald are classified as inclusions. Inclusions are any materials or substances trapped within a gemstone during its formation. They can take several forms, including crystals, minerals, or gas bubbles. The presence of actinolite needles within emeralds is an indicator of the gem’s natural growth process and is often used to identify the stone's origin and overall quality.

In this context, actinolite inclusions contribute to the character of the emerald, providing both aesthetic interest and important information regarding the gemstone's formation history. Understanding inclusions is crucial for gemologists, as they assist in distinguishing natural stones from synthetics or treated stones and can even impact the overall value and desirability of the emerald.