How Diamond Cutters Instantly Know Which Rough Stones Are Worth Millions

The First Step is Rough Evaluation

In the diamond industry, words like sawable, macle, makeable, splittable, and flat aren’t jargon—they’re essential tools of the trade. Diamond cutters live by these classifications, using them to determine whether a rough diamond is destined to dazzle or be relegated to industrial use.

The Critical Factor is Potential

Every rough diamond is judged by its potential as a faceted gem. The sorting process begins with a basic but crucial decision: is the rough cuttable (gem or near-gem quality) or non-cuttable (industrial quality)? Naturally, cuttable stones are far more desirable and valuable.

Shape Reigns Supreme in Value

Among all characteristics—clarity, colour, and weight—shape is the most decisive value factor for cuttable diamonds. Two stones with nearly identical weight, clarity, and colour can differ in value by a factor of ten simply because of their shapes. This is due to how shape determines yield, or how much faceted diamond can be recovered from the rough. For example, a 10-carat flat macle might produce just a few small baguettes, while a well-formed 10-carat octahedron could yield two round brilliants of 3.50 and 1.50 carats—an extraordinary difference in value.

Decoding Diamond Rough Types

To navigate this world of potential and precision, diamond cutters use specific terms

• Makeable: A whole stone that can be polished without any sawing or splitting. The final faceted shape closely mirrors the original rough.

• Sawable: A rough that will yield better results when sawn into two parts, maximizing retained carat weight.

• Splittable (or clivage): A stone that’s best divided into smaller segments through cleaving or laser sawing—often producing several small but high-quality gems.

• Macle: The most common twinned diamond crystal. Though tricky to cut, it can result in striking triangular brilliants with skillful handling.

• Flat: As the name implies, a thin, flat crystal with limited cutting potential—often producing only small stones or specialty shapes.

The Bottom Line

Rough diamond evaluation isn’t guesswork—it’s an art backed by decades of knowledge, deep experience, and a very particular vocabulary. To a trained cutter, the shape of a rough diamond speaks volumes, often spelling the difference between modest returns and multimillion-dollar treasures.