What is a blemish in the context of gemstones?

A blemish refers to a characteristic or irregularity that is found on the surface of a polished gemstone. These can include scratches, chips, or minor pits that alter the appearance of the gem but do not originate from within its structure. Blemishes can affect the overall visual appeal of a gemstone, influencing its perceived quality and value. Understanding blemishes is crucial in the evaluation of colored stones, as they play a significant role in determining clarity and therefore marketability.

The other options describe different aspects of gemstone characteristics or treatments. Internal inclusions relate to flaws within the stone that can affect clarity but differ from surface blemishes. Natural flaws that enhance value would imply that a blemish has positive attributes, which usually is not the case. Surface treatments involve processes applied to improve a stone's appearance, distinct from blemishes, which are unintentional imperfections.