How is the diamond mine recovery rate calculated, and what would constitute a high rate?

• A. Recovery rate equals the total number of diamonds mined.
• B. Recovery rate = saleable polished carats produced / total rough carats milled.
• C. Recovery rate equals the weight of waste material.
• D. Recovery rate is the price per carat of polished diamonds.

Answer: (B)

Recovery rate measures how efficiently the mine turns input rough material into saleable product. In diamonds, it’s defined as the weight of saleable polished carats produced divided by the total rough carats milled during processing. This captures losses that happen during cutting, polishing, sorting, and any material that isn’t saleable. So if you start with 1,000 rough carats and end up with 800 polished carats, the recovery rate is 80%, which would be considered high because a large majority of the input becomes marketable product.

This definition is the best because it directly reflects the physical conversion efficiency from input to final saleable output, rather than just counting how much ore was mined, how much waste was generated, or measuring economic value per carat. The other ideas—using total mined carats, the weight of waste, or price per carat—don’t measure how much of the input material is successfully converted into saleable diamond product.