Rough: Forms, Resorption, and Reading the Crystal

A rough diamond is not simply an “unpolished polished diamond.” Its external form, surface features, internal structure, and traces of dissolution together constitute a record of growth and later geological history—and also the starting point for a manufacturing plan.

Essential

A natural crystal can preserve primary growth forms, but during long residence in the mantle and especially during transport it can be partly resorbed. The present form of a rough diamond is therefore not necessarily the same as its form at the time of growth.

Octahedral, dodecahedral, and other forms must not be read as simple “quality types.” For planning, it is more important to understand:

• geometry and crystallographic orientation;
• whether the surface is primary or resorbed;
• where cleavage and fracture risks are located;
• how inclusions, strain, and color zoning are distributed;
• how reliably the external surface has been documented.

The Surface Speaks, but Not by Itself

Trigons, tetragons, etch channels, frosting, and hillocks can be traces of dissolution and resorption. They must be related to the crystallographic surface and context. Alluvial mechanical rounding is not the same as chemical resorption.

A radiation stain can be very shallow; its presence does not mean that the entire stone has the same color. Cleavage must be distinguished from irregular fracture and from a surface that was later polished.

On a polished stone, the term natural denotes a preserved portion of the original rough surface. It is not the same as an extra facet. A natural can be useful evidence of manufacturing history and orientation, but it should not be turned into an automatic judgment of quality.

How to Read Rough in Practice

A useful sequence is:

form → surface → interior → strain/color → risk → possible plans.

An external 3D scan can describe geometry very well, but it does not tell the entire internal story. Inclusions and fractures must be mapped in three dimensions. Color and strain can change the optimal orientation of the finished stone.

Rough is therefore not assessed only by weight and external beauty. One apparently small fracture can completely change the division line, while zoned color can justify a different shape or orientation.

What Rough Does Not Prove

Rough morphology can be strongly useful diagnostically, but by itself it is not universal proof of:

• the exact mine;
• full geographic provenance;
• the market value of the polished product;
• or even natural/laboratory-grown status in every possible case without other data.

A professional conclusion emerges from the combination of morphology, internal features, documentation, and laboratory analysis where necessary.

Practical Framework: Read Rough as a Record of Process

With rough, first separate the primary growth form from secondary resorption and fracture. Octahedral, cubic, and transitional geometries can reflect growth, while dodecahedroid surfaces, trigons, tetragons, frosting, or etch channels often record later dissolution. Rounding caused by chemical resorption should not be equated with mechanical wear during alluvial transport.

A macle is a contact twin, not merely “triangular rough.” Cleavage is a crystallographic fracture and must be distinguished from an irregular break or a polished plane. A natural on a polished stone denotes a preserved portion of the original rough surface and is not the same as an extra facet. These distinctions become important when planning orientation, division, and final weight.

A practical rough examination can proceed in this order:

1. document the external form and principal crystallographic faces;
2. record resorption and other surface features;
3. look for fractures, inclusions, and strain that can change the plan;
4. separate a radiation stain or surface color from color throughout the full volume;
5. only then assess possible polished outcomes.

Unusual natural materials further demonstrate why a name alone is not enough. Carbonado is a porous, strongly intergrown polycrystalline diamond with an unresolved primary source; ballas, bort, and other aggregates have different microstructures and use contexts. “Black diamond” is therefore not a synonym for carbonado, and natural polycrystalline material is not automatically technically superior to engineered synthetic PCD.

When to Escalate

Escalate when morphology, an inclusion, or geological context is being used to derive a precise mineral identity, age, pressure-temperature condition, depth, or geographic origin. Such conclusions require appropriate analysis and clearly stated uncertainty, not visual similarity alone.

Quick Check Before Reaching a Conclusion

Before accepting a technical, purchasing, or documentary conclusion, run this short check:

• Have I separated primary growth form from resorption, fracture, and transport?
• Am I distinguishing macle, cleavage, natural, and extra facet?
• Am I mapping fractures, inclusions, strain, and surface features before making a manufacturing plan?
• Am I treating a radiation stain as a surface feature until broader color is demonstrated?
• Am I avoiding the use of rough morphology as stand-alone proof of a mine or natural origin?

Common Mistakes

“Dodecahedral rough is simply another primary growth form.”
Many rounded dodecahedral forms are the result of resorption, so surface features and context must be read.

“Every trigon means the same thing.”
No. Its significance depends on the surface, orientation, and other features.

“A natural on a polished stone is an extra facet.”
No. A natural is preserved original rough surface.

“If rough looks like a known local population, we know the mine.”
No. Similar morphology can develop in different geological systems.

Remember

Rough is read systematically. The most useful information does not come from one “recognizable” surface feature, but from the relationship among form, resorption, interior, crystallography, and manufacturing risk.

Go Deeper in The Book

• Chapter 12 — Unusual Natural Forms
• Chapter 13 — Rough Diamond: Reading an Uncut Crystal