DiamondAvenue.com - Facts About Rough Diamonds
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Whole Rough Diamonds

Some rough diamonds retain much of their original crystal form but show modifications caused by natural growth, resorption, erosion or breakage.

These crystals may exhibit characteristics of octahedral, dodecahedral or cubic forms while also displaying rounded faces, softened points, ribs or other altered surfaces.

The term whole rough has traditionally been used in parts of the diamond trade for crystals that remain substantially intact rather than occurring primarily as broken fragments.

Irregular Rough Diamonds

Not every rough diamond retains an easily recognizable geometric crystal shape. Some specimens are elongated, distorted, broken or otherwise irregular.

Irregular rough may result from unusual crystal growth, natural cleavage, breakage or resorption before the diamond reaches the Earth's surface.

These unusual shapes can present both challenges and opportunities for diamond cutters because the finished stones must be planned around the available rough material.

Alluvial & River-Deposited Rough Diamonds

Some diamonds are recovered far from the volcanic source rocks that originally carried them toward the Earth's surface. Over long periods of time, weathering can release diamonds from their host rock and transport them through streams and rivers.

Diamonds concentrated in river gravels, ancient river channels, coastal deposits and similar secondary deposits are generally referred to as alluvial diamonds.

During transport, some rough crystals may experience abrasion, breakage and continued natural modification. Rounded or worn surfaces can therefore provide clues about a diamond's geological history, although the appearance of any individual crystal can result from several different natural processes.

Size

Rough diamonds are weighed in carats and may also be separated into size ranges before additional sorting and manufacturing decisions are made.

Shape

Octahedrons, dodecahedrons, cubes, macles, fragments and irregular crystals can require very different cutting strategies.

Color

Rough may appear colorless, yellow, brown or exhibit other natural colors. Color distribution can influence how the finished diamond is oriented and cut.

Clarity

Inclusions, fractures and other internal characteristics are studied to determine how they may affect the appearance, durability and value of the polished stone.

Sawable Rough

Sawable rough consists of crystals that can benefit from being divided before polishing. Octahedral and other suitable rough may be sawn into two sections so that each section can be fashioned into a polished diamond.

The location of inclusions, the natural shape of the crystal and the potential polished yield all influence where the rough is divided.

Makeable Rough

Makeable rough can generally be fashioned into a single polished diamond without first dividing the crystal into major sections.

The cutter works with the existing shape of the rough and removes material as necessary to create the desired polished form and proportions.

Cleavage Rough

Diamond has natural directions along which its crystal structure can split. Historically, cleaving was an important method of dividing suitable rough diamonds.

Whether rough is cleaved or sawn depends on factors including crystal orientation, shape and the location of inclusions.

Macles

Macles are twinned diamond crystals that often have a flattened triangular form.

Their unusual geometry requires specialized planning because the orientation and thickness of the rough affect which polished shapes can be recovered.

Flats & Chips

Thin crystals, fragments and pieces created through natural breakage may be grouped into categories such as flats and chips.

Although they may lack the symmetry of complete crystals, suitable pieces can still have useful gem-cutting potential.

Modern Planning

Modern manufacturers can scan rough diamonds and map inclusions before cutting begins.

Computer-assisted planning allows cutters to compare different combinations of polished shapes, sizes, clarity outcomes and potential values before deciding how to process the rough.

Gem-Quality Rough

Gem-quality rough has characteristics that make it suitable for cutting and polishing into diamonds intended primarily for jewelry.

Important considerations include color, transparency, clarity, crystal shape, inclusions and the expected yield of attractive polished diamonds.

Even a rough crystal containing inclusions may yield a desirable finished diamond if those inclusions can be removed or strategically positioned during cutting.

Industrial Diamond

Diamonds unsuitable for conventional jewelry can still be extremely valuable as industrial materials because of diamond's exceptional hardness and resistance to wear.

Industrial diamond has historically been used in applications involving:

• Cutting tools
• Grinding and machining
• Drilling equipment
• Abrasives
• Polishing compounds
• Precision manufacturing

Boart

Boart, also spelled bort, traditionally refers to low-quality diamond material that is not suitable for cutting into conventional gemstones.

Such material can be crushed or processed into diamond grit, powder and abrasive products.

Diamond abrasive has historically been important in polishing diamonds themselves as well as in numerous industrial cutting and finishing operations.

Why There Is No Single Gem-to-Industrial Percentage

Older references sometimes divide worldwide rough diamond production into fixed percentages of gem-quality, industrial-quality and boart material. In practice, the proportions can vary considerably according to the mine, geological deposit, parcel, crystal sizes and the standards used to classify the material.

Modern cutting technology can also affect the economic potential of individual rough diamonds. Sophisticated planning systems may identify valuable polished stones in rough that would previously have been more difficult to manufacture efficiently.

Thousands of Sorting Categories

Rough diamond classification can become extraordinarily detailed when size, shape, color, clarity and quality are considered together.

Major historical sorting operations have used thousands of individual categories to create parcels of rough diamonds with similar characteristics.

Individual manufacturers normally use fewer categories, selecting the classifications that are most useful for the types and quantities of rough they process.

The Goal: Best Use of the Rough

The ultimate goal of rough diamond planning is to determine the most advantageous way to transform a natural crystal into polished diamonds.

Manufacturers evaluate potential finished weight, diamond shape, clarity, proportions, market demand and overall value rather than concentrating on carat weight alone.

As a result, two rough diamonds of similar weight may require completely different manufacturing strategies.