Which type of rough is most likely to undergo cobbing?

Cobbing is a technique used primarily in the gemstone industry to improve the quality of rough stones by removing undesirable parts of the material before cutting. This process helps maximize the yield of polished gems and ensures that only the best portions of the rough are utilized in the final product.

Commercial-quality amethyst rough is well-suited for cobbing because it often contains inclusions, color zoning, or other imperfections that can be eliminated to enhance the overall appearance and value of the finished stones. This type of rough is typically processed in bulk, and cobbing allows gem graders and lapidaries to efficiently extract high-quality material from larger pieces.

In contrast, high-grade diamond rough is usually valued for its exceptional clarity and quality, which requires more careful cutting techniques rather than copious removal of rough material. Artisan-quality jade rough is often worked with more emphasis on preserving the stone's natural structure and artistry, which could limit the use of cobbing. Lastly, semi-transparent opal rough may have distinct color patterns that are desirable, and excessive cobbing would risk losing the unique characteristics that make these stones attractive.

Thus, amethyst rough stands out as the type most likely to benefit from the cobbing process due to its common inclusion issues and the potential for improvement