Diamonds are one of the most precious and valuable gemstones in the world. Diamonds are formed naturally deep within the earth under extreme heat and pressure over billions of years. Rough diamonds are then mined from volcanic pipes or alluvial deposits before going through extensive processing and cutting to produce the sparkling finished diamonds used in jewelry.
Cutting and polishing raw diamonds into brilliant gems suitable for jewelry requires expertise and precision. Skilled diamond cutters analyze each rough stone to determine the ideal cut that will maximize carat weight, color, clarity and overall beauty. However, cutting and polishing a diamond does result in some weight loss. The amount of loss varies depending on the unique characteristics of each rough stone.
How Are Diamonds Cut?
Diamond cutting is a complex process that requires skill, experience and specialized tools. The goal is to transform an irregularly shaped rough diamond into a finished gemstone that showcases optimal light refraction, sparkle and fire.
Cutters will examine the rough diamond to identify inclusions and imperfections. They determine the optimal shape to cut based on the natural shape and grain structure. Round brilliant cuts are the most common, but diamonds can also be cut into many other shapes like princess, cushion, oval, marquise, pear or heart shapes.
The diamond is marked and cleaved or sawed along the grain lines. This removes large rough sections of the stone while attempting to preserve as much weight as possible. The cutter uses a tool called a dop stick to grip the diamond securely while working.
The specific faceting process will vary depending on the desired finished shape. The outline is shaped by faceting the ‘girdle’ of the stone. More facets are added above and below the girdle to create the crown and pavilion. The diamond is set at precise angles within the dop stick during cutting to ensure proper symmetry and proportions. Lasers and computer modeling are sometimes used to maximize accuracy.
Finally, the diamond is polished to add shine and luster. A coarse polishing wheel first smooths and shapes the facets. Fine polishing using diamond grit removes fine scratches and sculpts the intricate facet edges. The completed diamond is carefully inspected to confirm quality standards are met before being set into jewelry.
Weight Loss During Cutting
The amount of weight lost when cutting a rough diamond depends on several factors:
– Size of the rough stone – Larger carat weights have more wastage
– Quality – Lower quality rough with more flaws requires more cutting
– Cut quality – Finer cuts with more facets require removing more material
– Shape – Round brilliant cuts tend to lose more than other shapes
On average, about 50% of a rough diamond’s total carat weight is lost during cutting. Some examples:
– A 5 carat rough diamond may lose 2-3 carats, yielding a polished 2-3 carat round brilliant.
– A 1 carat rough may become a 0.50 carat princess cut.
– A 0.25 carat rough could produce a 0.15-0.18 carat cushion cut stone.
Optimizing Yield
Diamond cutters take steps to maximize yield and conserve as much carat weight as possible when cutting rough diamonds:
– Analyzing the rough stone carefully to identify best shape and faceting approach.
– Cleaving and sawing selectively along grain planes, not haphazardly.
– Placing priority on quality, not just weight retention. Removing flaws improves value.
– Using computer modeling to achieve ideal cut with least waste.
– Precision cutting with minimal overcutting at facet junctions.
– Polishing carefully without removing more material than necessary.
– Recutting/repolishing diamonds that perform poorly.
Still, to uncover a diamond’s full beauty, brilliance and fire, some weight loss is unavoidable. The cut is far more important than carat weight alone when determining a diamond’s value. Even with significant weight loss, cutting can unveil a rough diamond as a spectacular gem.
Does Cut Quality Affect Weight Loss?
Yes, the quality of the cut will directly impact how much material is removed from a rough diamond during faceting and polishing.
Diamond cutting has advanced significantly in the last century. Older diamond cuts required removing more rough diamond to complete. Significant developments like diamond sawing, bruting machines, and laser cutting enabled more precision with less waste.
Some examples comparing weight loss on different quality cuts:
Old Mine Cut
– Also called “Old European” cut
– Thick facets, narrow tables, high crowns
– Less precise, deeper cut to conserve carat weight
– Still lost ~50-60%
Modern Round Brilliant Cut
– Proportions designed for maximum brilliance
– Wider tables, lower crowns, precise angling
– Computer modeling optimizes design
– Loses ~50%
Ideal Cut
– Superb workmanship and precision
– Cut for “hearts and arrows” light pattern
-Very specific crown/pavilion angles
– Only top ~1% of diamonds
– May lose up to 60% of rough weight
So while an ideal cut may result in slightly more waste from the rough stone, this is because it is cut with supreme precision to achieve the best possible performance. The end result will be a dramatically more beautiful and valuable diamond.
Impact of Diamond Shape on Weight Loss
The shape of the finished diamond will also influence total weight loss from the rough stone. This is because different shapes require different faceting:
Round Brilliant
– Most popular diamond shape, makes up ~75% of all diamonds
– Cut with 58 facets
– Designed to maximize light return and sparkle
– Requires a precise girdle outline and angled facets
– Tends to lose about 50% of rough weight
Princess Cut
– Square shape with pointed corners
– Usually 80-100 facets
– Retains more weight from roughs with square outlines
– Amount lost can be closer to 35-40%
Cushion Cut
– Gently rounded square/rectangular shape
– 62-64 facets
– Not as dependent on square roughs as princess cuts
– Average loss is around 45%
Oval Cut
– Elliptical outline with 58 facets like round
– Oval roughs can yield ovals with less loss
– Loss averages 50% but can be less
Marquise Cut
– Long tapered outline with 58 facets
– Cut to retain elongated shape of rough
– Loss also averages around 50%
So while the round brilliant tends to lose the most weight from rough to finished diamond, shapes like princess and oval that retain the rough outline lose comparatively less. But shape alone does not determine cut quality or value.
Does a Diamond’s Clarity Affect Cutting Loss?
Yes, the clarity grade of a rough diamond can impact the amount of weight lost when cutting and polishing the stone.
Diamonds with lower clarity grades have more inclusions and blemishes internally. To remove these defects, cutters must bear more deeply into the stone, sacrificing more carat weight. Rough diamonds with higher clarity grades have fewer flaws, allowing for less waste during cutting.
Some examples:
Rough Diamond Clarity: I3
– Heavily included, obvious blemishes
– Cutting to remove inclusions sacrifices weight
– May lose 60-70% from rough to polished
Rough Diamond Clarity: SI2
– Still visibly included under 10X magnification
– Requires removing some inclusions during cutting
– Loss is closer to the average ~50%
Rough Diamond Clarity: IF
– No inclusions visible, very rare
– Can be cut with minimal weight loss
– May only lose 40-45%
Maximizing a diamond’s clarity during cutting often requires losing more weight. But removing undesirable inclusions has a far greater impact on the end value than just retaining carat weight alone. Like cut, optimized clarity outweighs size.
Impact of Color Grade on Diamond Cutting Loss
A diamond’s color grade does not have a direct impact on the amount of weight lost when cutting and polishing. However, removing body color in lower color grade rough diamonds can influence cutting decisions.
Diamonds graded D-F are considered colorless. There is no noticeable body color, so cutting to minimize color is unnecessary. Weight retention would be based on other factors like clarity and cut quality.
As color grade drops, subtle yellow and brown hues start to appear in G-I grades. For these diamonds, cutters may strategically remove some areas of heavier color concentration, though overall loss is still similar.
In lower color grades like J-R, the yellow/brown tint is more obvious. Here, cutters may bear deeper to eliminate or reduce noticeable color areas. But this is done with discretion since removing too much weight can negatively impact value.
So for faintly colored diamonds, decisions about eliminating undesirable color areas can lead to slightly higher average weight loss closer to 55%. But the tradeoff produces better color that adds value.
Does Cutting Improve Diamond Grade?
Cutting and polishing rough diamonds into finished gems does not improve the inherent color or clarity grades. The existing mineral structure and impurities remain unchanged. However, cutting does often allow color and clarity to be displayed in a more favorable way.
Here are some examples of how cutting can showcase color and clarity grades better:
– Strategic cutting removes heavily concentrated inclusions, improving apparent clarity.
– Skillful facet placement and angling mask remaining inclusions.
– Eliminating areas of undesirable body color minimizes visible color effects.
– Appropriate shaping avoids leakage of color through certain crystal directions.
– Finished diamonds “face up” whiter compared to rough stones.
So while cutting a diamond does reduce carat weight, the tradeoff is considerably improved sparkle, brilliance, and aesthetic appeal. The ultimate beauty and value lies in skillful cutting and polishing – not just retaining maximum carat weight.
Factors That Help Preserve Diamond Weight During Cutting
While most rough diamonds lose close to 50% of their weight when cut, there are some tactics cutters use to help retain as much carat weight as possible:
– Laser sawing/cleaving – More precise than physical sawing alone. Causes less collateral fractures.
– Computer scanning and modeling – Maps rough stone and simulates ideal cut with minimal waste.
– Bruting – Specialized machine safely rounds and shapes diamonds through friction. Less risky than shaping by hand.
– Maximizing rough utilization – Getting multiple finished diamonds from crystal cleavages and fragments that would normally be waste.
– Recutting/repolishing – Further enhancing poorly performing cut diamonds instead of recarving them from scratch.
– Minimal polishing – Restricting final polish to essential areas only, without overpolishing.
– Selecting rough carefully – Choosing rough diamonds with shapes allowing better yield.
– Cutting for carat weight – Prioritizing carat retention, though this risks lower cut quality.
– Less facets – Shapes like baguettes with fewer facets retain more weight than brilliant cuts.
However, most experts caution against putting too much priority on carat weight retention alone. Optimal cutting should focus mainly on unlocking a diamond’s full potential beauty and value.
What Happens to Diamond Cutting Waste?
The leftover diamond powder created during faceting and polishing is too fine to be used in jewelry. However, virtually all diamond waste is recovered and repurposed in various industrial applications.
– Abrasives – Diamond grit is superior for grinding, drilling, sawing, and polishing other hard materials.
– Oil/Gas drilling – Diamond cutters penetrate rock for oil/gas extraction.
– Mining – Diamond extraction and crushing hard ore.
– Construction – Cutting concrete, stone and asphalt.
– Glass & optics – Polishing lenses, prisms and optical elements.
– Circuit boards – Polishing silicon chips and semiconductors.
– Medical – Scalpels, dental burs, laser surgery components.
So while rough diamonds sacrifice significant weight to become dazzling jewelry, the leftover material enjoys a productive second life serving diverse industrial needs. Virtually no natural diamond material is wasted.
Conclusion
Transforming diamonds from rough stones to brilliant gems suitable for jewelry requires immense skill and inherently involves weight loss. On average, about 50% of a rough diamond’s weight is removed during the cutting and polishing process. This percentage can vary based on the stone’s carat weight, clarity, desired cut, and other factors.
Cutters employ numerous techniques to conserve as much weight as possible when faceting diamonds. However, retaining maximum carat weight should not override optimizing for cut quality and overall beauty. While carat weight lost may seem high, keep in mind the exponential increase in dazzle, sparkle and value unlocked from a diamond cut to ideal proportions. What is sacrificed in size is gained in perfection, scintillation and visual impact.