Diamond Polish: Grading, Price Impact, and Polishing Techniques

What gives a diamond its captivating brilliance and fire? Cut is the top factor, but closely following is diamond polish. This finish given to a diamond’s facets greatly impacts its beauty and value.

What is Diamond Polish on a Grading Report

Diamond polish is a crucial aspect of diamond quality. It refers to the smoothness and shine achieved through precision cutting and polishing techniques. A well-polished diamond enhances its brilliance, sparkle, and overall beauty, making it highly desirable for jewelry pieces.

The polishing process is one of the final steps in preparing rough diamonds for jewelry. During polishing, facets are buffed to a high gloss using abrasives and polishing discs or wheels. The result is a smooth, mirror-like surface that allows light to reflect brilliantly off the diamond.

This article will cover the importance of diamond polish in determining quality and price. You’ll learn how GIA (the Gemological Institute of America) grades polish and what specific characteristics the graders evaluate. We’ll also discuss the relationship between polish, symmetry, and achieving optimal light performance. Let’s start by understanding the GIA’s diamond polish grading scale.

Grading a Diamond’s Polish

GIA grades polish on a scale ranging from Excellent to Poor. Where a diamond falls on the scale depends on the smoothness of its facets, quality of its shine, and the number of surface blemishes visible under 10X magnification. Here is a breakdown of each GIA grade:

Excellent – Reflects the maximum amount of light due to perfectly smooth, glossy facets with no scratches or surface blemishes. This flawless polish represents expert craftsmanship. Less than 1% of diamonds receive the Excellent grade.

Very Good – Smooth and reflective but with a few minute scratches and small surface imperfections. Around 15% of diamonds receive Very Good grades.

Good – Noticeably less reflective and smooth compared to higher grades, with lightly scratched facets and/or minor pits or nicks. Over half of all diamonds receive Good polish.

Fair – Abundant scratches that diminish light return, along with obvious pits and nicks visible upon close inspection. Nearly 25% of diamonds receive Fair grades.

Poor – Severely scratched facets that act as windows, allowing light to leak out rather than reflect back. Visible surface grains and large nicks and pits. Found in 5-10% of diamonds, mostly in smaller melee accent stones.

The better the polish, the more brilliant the diamond will appear. Diamonds with lower polish grades lose light through the rough, scratched facets. This noticeably diminishes brightness and fire. As you’ll see next, excellent polish has a major impact on diamond value.

How Polish Impacts Diamond Price

Diamond polish significantly influences gem value, with prices jumping at each grade level. A 1 carat round diamond may sell for:

– Excellent: $7,600
– Very Good: $6,500
– Good: $5,200
– Fair/Poor: $3,400

As these prices show, a diamond with excellent polish rather than good may command a 45% premium. The difference between excellent and very good polish is roughly 15%. Even a jump from good to very good may add 25% to the value.

Polish has a more pronounced impact on value in step-cut diamonds like Emeralds and Asschers. Well-polished facets are highly visible in these shapes. On the other hand, brilliance is spread across more facets in Brilliant Cuts like rounds and cushions. With these styles, inclusions often impact price more than polish.

Now that you know how much polish influences value, let’s examine the complex process of polishing diamonds.

The Diamond Polishing Process

While diamond cutting originated in the Middle Ages, diamond polishing only came into its own in the late 1800s. As engineers created improved polishing laps and compounds, they brought forth today’s brilliance standards.

The polishing stage begins after the diamond cutter shapes and facets the rough stone into a nearly finished gem. The lapidary first examines the diamond under magnification to plan the polishing approach. Some facets may require more work than others to achieve uniform smoothness.

The diamond is attached to a dop stick with solder or adhesive. The dop sticks are then fixed to rotating polishing laps infused with diamond abrasives. Two well-known options are lead laps embedded with diamond dust and scaife laps crafted from naturally abrasive Belgian whetstone.

As the lap spins, it presses against the diamond to smooth out scratches and shape the facets’ curves. Progressively finer abrasives are used until the last polishing stage, which imparts the final high gloss. Depending on the complexity of the cut, polishing may take several hours to multiple days.

After polishing, the gem undergoes microscopic inspection and a careful hand wash. Manual inspection weeds out diamonds with significant blemishes that warrant re-polishing. As you’ll see next, symmetry faults can also necessitate additional work.

How Symmetry Impacts Polish Results

Diamond symmetry refers to the alignment and precision of facets across the stone. Are opposite facets mirrored exactly? Do the points and edges line up? How consistent are the angles and curves?

GIA grades symmetry on an Excellent to Poor scale similar to polish. The highest grades go to diamonds with perfect facet symmetry. Diamonds with slightly misaligned facets or small variations in angles/curves receive Very Good or Good grades. Obvious inconsistencies result in Fair or Poor.

Diamonds must have very good symmetry to achieve excellent light performance. Even minor deviations can prevent light from reflecting cleanly back to the eye. The results are noticeable dips in brilliance and fire.

This means the polish grade is heavily influenced by the underlying symmetry. A diamond with poor symmetry limits how smooth and gleaming the polisher can make the facets. The best polish comes from expert planning before the first cut enters a rough diamond.

Common Questions About Diamond Polish

Does polish make a diamond more brilliant?

Yes, diamond polish is a significant component of brilliance. Well-polished facets allow more light to cleanly enter, refract, and return to the eye as sparkling brightness.

Do all diamonds have some polish issues?

Polish imperfections are common even among high quality diamonds. Around 85% grade Good to Very Good. Visible scratches and pits are typically minute, not marring beauty.

Can polish be restored by cleaning/polishing at home?

Home techniques effectively remove small scratches and dull spots. But extensive wear or re-cutting requires professional equipment and expertise.

How much does polish affect the diamond’s value?

On average, each climb in GIA polish grade adds 10-15% to the diamond’s price. Excellent polish commands premium pricing, sometimes up to 40% over a Good grade.

Can a poorly polished diamond be re-cut to improve polish?

Yes, re-cutting and re-polishing can improve lackluster diamonds. But this reduces carat weight and may lower clarity or color. Generally, re-polishing poses less risk.

Does an Excellent polish grade guarantee a flawless diamond?

Not necessarily. While far fewer Excellent diamonds have visible inclusions, polish only assesses smoothness and shine of facets. Clarity grading determines flaws.

Does the polish grade include the whole diamond or just the top/crown?

GIA assesses polish over the entire diamond. However, the crown’s polish is most important for brilliance while the pavilion strongly impacts fire and scintillation.

How Diamond Polish Affects Price

Diamonds with Excellent polish fetch the highest prices. Even well-cut diamonds must have exemplary polish to qualify for top value grades.

Price drops significantly for Fair to poor polish grades. Most diamonds graded Fair/Poor are accent stones due to their noticeably dull appearance.

There are large differences in price for Excellent vs. Very Good polish. On 1 carat rounds, it may be $1,000+ higher for Excellent when all else is equal.

Certain shapes like Emerald cuts show more facets at once. This makes polish highly visible so customers pay more for Excellent.

Depending on size and other factors, Excellent polish may command a 15-40% premium over Good. Prices jump 10-15% between other grade levels like Very Good and Good.

Some sellers use Excellent polish to justify escalated pricing on diamonds with only so-so cuts. Always judge brilliance, not just the report.

A Fair or Poor polish grade may be acceptable for melee accent diamonds. But never compromise polish on center stones or visible main diamonds.

Key Takeaways

In summary, try to buy diamonds with the highest polish grade within your budget.

Prioritize Excellent polish for important shapes like rounds and Emeralds.

With proper care and occasional polishing, your diamond will maintain its sparkling finish and value.

Carl A. Jones, GIA GG

Carl A. Jones is a GIA Graduate Gemologist with over 20 years of experience in the diamond industry. He is an independent jewelry appraiser. He specializes in determining the value of diamonds and advising consumers on how to buy quality diamond jewelry.

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