What term refers to the quality ranking of gemstones based on specific criteria?

The term that refers to the quality ranking of gemstones based on specific criteria is "Grade." In the context of colored stones and gemology, grading involves assessing various attributes such as color, clarity, cut, and carat weight to determine the overall quality of a gemstone. This grading is essential for appraisals and market values, as it provides a systematic way for gemologists and buyers to understand the relative merits of different stones.

While "quality standard," "gem classification," and "quality metric" may also relate to gemstone evaluation, they do not specifically define the ranking system used to categorize a gemstone's quality. "Quality standard" may refer to a set of benchmarks or guidelines but does not directly imply a ranking. "Gem classification" is more about categorizing stones into types or families rather than assigning a quality score. "Quality metric" might refer to measurements that help assess quality, but again, it doesn't encompass the systematic ranking that "Grade" implies. Therefore, "Grade" is the precise term that encompasses the ranking aspect in the context of gemstone evaluation.