Cleavage rough is a category of diamond rough in which one or more flat cleavage surfaces are already present, either as a result of natural fracturing within the host rock, mechanical stress during blasting and extraction, or deliberate splitting carried out at the mine or sorting facility. Because diamond cleaves perfectly along its octahedral planes — the {111} crystallographic directions — any break along these planes produces a characteristically smooth, mirror-like face quite unlike the conchoidal fracture seen in most other minerals. That surface is the diagnostic signature of cleavage rough, and it is what separates this material from the two other principal categories of diamond rough used in the trade: sawables (well-formed octahedra or near-octahedra suited to sawing) and makables (irregular crystals that must be cleaved or sawn before fashioning).

Why Cleavage Surfaces Matter to the Cutter

Diamond's perfect octahedral cleavage is both its most useful and most treacherous property. A cutter working with an intact crystal has maximum freedom in orienting the stone to optimise weight retention, symmetry, and the avoidance of inclusions. Cleavage rough, by contrast, arrives with at least one plane already fixed. The cutter must respect that existing surface — or risk propagating the cleavage further — which constrains the range of possible cutting orientations. In practice this means lower weight retention relative to the original rough, a reduced ability to steer around internal flaws, and, in some cases, a ceiling on the finished stone's potential size. A large cleavage piece may still yield a significant polished diamond, but the path to that outcome demands more skill and more careful planning than an equivalent weight of intact sawable rough.

Grading and Pricing in the Rough Diamond Trade

The rough diamond market sorts goods into a hierarchy that broadly reflects cuttability and expected polished yield. Sawables command the highest prices per carat because they offer the greatest flexibility. Makables trade at a discount to sawables. Cleavage rough sits below both, attracting a further discount that reflects the constraints described above. The magnitude of that discount depends on several factors:

• Number and orientation of cleavage surfaces. A single clean cleavage on an otherwise sound piece is far less penalising than multiple intersecting planes, which can reduce the stone to a collection of small, awkwardly shaped fragments.
• Size of the piece. Large cleavage rough — material that can still yield a polished stone of a carat or more — trades quite differently from small cleavage chips destined for melee or industrial use.
• Colour and clarity of the underlying crystal. High-colour, high-clarity cleavage rough retains considerable value despite its limitations; heavily included or off-colour material is discounted steeply.
• Stability of the cleavage surface. A fresh, stable cleavage is preferable to one that shows feathering or secondary cracking, which signals a higher risk of further breakage during polishing.

Natural versus Induced Cleavage

Not all cleavage rough originates the same way. Natural cleavage occurs underground, where tectonic stress, thermal cycling, or the violence of kimberlite emplacement splits crystals along their octahedral planes before they ever reach the surface. Such pieces are recovered already cleaved from the ore body. Induced cleavage, by contrast, is introduced during mining — by blasting, by the mechanical action of crushers and scrubbers, or occasionally by deliberate splitting at the mine to remove a large inclusion or to separate a twinned crystal (macle) into more workable portions. The trade does not always distinguish sharply between the two origins, since the resulting rough presents the same cutting challenges regardless of how the surface was formed.

Relationship to Macles and Twinned Crystals

The related term macle — a flattened, triangular diamond twin — is sometimes confused with cleavage rough because macles are also sold at a discount and require specialised cutting. The distinction is important: a macle is a twinned crystal whose flat appearance arises from its growth habit, not from cleavage. Cleavage rough, by definition, has been broken. A macle that has subsequently been cleaved to remove a damaged zone would qualify as both, but in ordinary trade usage the two categories remain separate.

In the Trade

The term is standard in the rough diamond sorting rooms of Antwerp, Mumbai, Surat, and Tel Aviv, as well as in the tender and auction systems operated by major producers. Sight holders and rough dealers encounter cleavage rough routinely in mixed parcels, where it must be identified and valued separately from sawables and makables. For smaller cutting centres that specialise in lower-cost melee production, cleavage rough — particularly small cleavage chips — represents a significant portion of the input material, since the yield constraints that penalise large-stone cutting are less critical when the target is one- or two-millimetre rounds. In this segment of the market, cleavage rough is purchased deliberately rather than merely tolerated.