The diamond cutting process
The cutter decides where the weight goes. You decide whether that weight gives you visible size, useful brightness, or a bigger number on the report.
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From rough to polished
The plan decides what survives the cutting wheel. The cutter works around the crystal’s shape, inclusions, and grain direction. These five stages group the full process, including marking and brillianteering. No single yield percentage promises quality.
Computer software helps compare possible shapes and map inclusions. The marker then outlines the cutting plan on the rough. That plan balances finished size, clarity, proportions, and the value of the stones it can produce.
Your buying question Did the final plan prioritize appearance or just a weight target?
One rough crystal can produce several polished diamonds. A saw or laser separates the pieces. Cleaving splits suitable rough along a natural cleavage plane. The crystal and its inclusions help determine the route.
Your buying question What did the cutter remove, and what remains inside the finished stone?
Bruting rounds the outline and forms the girdle, the rim between the crown and pavilion. Traditional bruting uses one diamond against another. Fancy shapes need their own outline and facet layout.
Your buying question Does the outline look balanced, with useful visible spread?
Blocking establishes the main facets. Brillianteering adds the smaller facets that complete a round brilliant’s pattern. Their placement matters too. The main angles alone do not tell you how the finished stone will look.
Your buying question Do the facets work together, or did a depth target dictate the result?
Clean the diamond. Check the finish, proportions, and remaining features. If the result needs work, the cutter can return it to polishing before the final assessment.
Your buying question Do the report and actual appearance support the price?
The main facets set the framework. The smaller facets finish the pattern. GIA’s diagram shows both, alongside the angles and dimensions that shape the finished diamond. Use it to see where the cutter keeps or removes weight.
View full-size diagramDiagram: © GIA. View the source chart.Technical background: Modern Diamond Cutting and Polishing. Equipment has developed since this publication; it explains the core manufacturing stages rather than every current machine.
Compare GIA’s standard arrangement with crown painting and digging out at the girdle. These are cutting variations, not surface coatings.
The bezel and half facets meet the girdle at roughly equal thicknesses, creating an even scalloped edge.
View full-size diagramDiagram: © GIA. View the source chart.
Tilting the upper half facets toward the bezels changes the junctions.
Diagram: © GIA. Read the explanation.
Tilting the half facets away from the bezels or pavilion mains changes the junctions at the rim.
View full-size diagramDiagram: © GIA. View the source chart.Check the actual light pattern. The effect depends on the proportions and the extent of the change.
The weight tradeoff
Carat measures weight. Diameter and outline describe visible size. A deep pavilion or very thick girdle can keep weight in places you do not appreciate from above.
Imagine two round diamonds with similar carat weights. One spreads wider; the other carries more depth. You need the millimeter dimensions and the light pattern to decide which is the better buy. This is a comparison method, not a claim that shallow always wins.
Too thin raises durability concerns. Too thick can carry weight without useful spread. GIA’s chart shows the difference across eight girdle categories. The percentages are typical examples for symmetrical diamonds with evenly scalloped girdles. Ask how the rim works with the shape and setting.
View full-size diagramDiagram: © GIA. View the source chart.The features the plan leaves behind
Changing the outline or removing material can reduce an inclusion’s effect. It can also leave a feature near a girdle or vulnerable point to preserve weight. Clarity grade alone does not tell you whether that tradeoff works for your setting.
Give a bruise, chip, cavity, knot, etched channel, or indented natural specific attention. Ask where it sits, whether it reaches the surface, and what a qualified inspection says about durability. A plot or video cannot settle every concern.
An inclusion that does not catch your eye can still need a durability review. Appearance and structural questions are different.
Recutting removes weight and changes the diamond. Ask for a specialist’s plan, costs, risks, and fresh grading rather than assuming an upgrade is automatic.
Apply the process to a purchase
For a natural diamond, start with GIA. Match the shape, measurements, grades, comments, and identity.
Start near table 56 to 58 percent, depth 60 to 62.4 percent, crown angle 34 to 35 degrees, and pavilion angle 40.6 to 41 degrees. Prefer Excellent polish and symmetry and none to faint fluorescence.
Use video under ordinary light and useful optical evidence. Screening ranges do not guarantee appearance and do not apply to fancy shapes.
Confirm a return window long enough for verification. Do not pay a premium for a manufacturing story without evidence for the actual stone.
Put the GIA cut grade in context and see what physical verification has uncovered.
Straight answers
Diamond powder does the abrasive work. A metal wheel called a scaife carries the powder with oil. The cutter holds each facet at a controlled angle against it. Crystal grain affects the directions that will take a polish.
Either is normal. A standard round brilliant has 57 facets, or 58 if the cutter adds a culet facet at the bottom. That extra facet does not automatically make it better. Check how the whole pattern handles light.
No. Lasers can help separate or shape material. Faceting and polishing still involve precise work on the diamond’s surfaces, with equipment and technique varying by operation.
No. Yield depends on the crystal, inclusions, chosen shape, and plan. Inspect the finished proportions and appearance. A loss percentage does not grade the diamond.
Sometimes, but get a specialist’s assessment first. It removes weight and carries cost and damage risk. Compare the proposed appearance improvement with the entire tradeoff.
No. Polish evaluates surface finish. Overall cut evaluates a broader set of factors. Read the separate report fields before comparing stones.