The Diamond Certification Laboratory of Australia (DCLA)

The nailhead effect refers to an unattractive black or dark shadow that appears under the center of a round brilliant cut diamond when its pavilion (lower portion) is too deep. This phenomenon makes the diamond look dull and lifeless, significantly reducing its brilliance and sparkle.

What Causes the Nailhead Effect?
Excessive Pavilion Depth

When a diamond’s pavilion is too deep, light entering through the crown (top portion) does not reflect properly.
Instead of bouncing back to the viewer’s eye, the light leaks out through the sides or bottom, creating a dark or black appearance in the center.
Reflection of the Table Facet

The dark shadow is often a reflection of the diamond’s table (the large flat facet on top) due to improper light return.
Instead of sparkling, the center appears dull, almost like a black “nailhead” at the heart of the diamond.
Poor Cut Proportions

Diamonds with incorrect depth-to-table ratios or poor symmetry are prone to the nailhead effect.
Ideal cut proportions ensure maximum brilliance by optimizing light reflection and refraction.
How to Avoid the Nailhead Effect?
Choose an Ideal-Cut Diamond:
Look for excellent or ideal cut grades, as these ensure proper pavilion depth and light performance.
Check Pavilion Angle:
A well-cut round brilliant diamond should have a pavilion depth of around 42.5%–43.5% of the total depth.
Observe the Diamond Under Different Lighting:
Rotate the diamond and view it under various lighting conditions to check for unwanted dark areas.
Get a Professional Grading Report:
Certification from laboratories like DCLA, GIA, or AGS will help verify the diamond’s proportions and cut quality.
Nailhead vs. Fish-Eye Effect
Nailhead Effect: Occurs when the pavilion is too deep, creating a dark shadow in the center.
Fish-Eye Effect: Happens when the pavilion is too shallow, causing an unattractive white or gray ring reflection inside the diamond.

A natural refers to a portion of the original rough diamond’s outer surface that remains unpolished on a finished, faceted diamond. This feature is intentionally left on the stone during the cutting and polishing process and is typically found along the girdle—the outer edge of the diamond that separates the crown (top) from the pavilion (bottom).

Why Are Naturals Left on a Diamond?
Maximizing Carat Weight

Diamond cutters aim to retain as much of the rough stone as possible. Removing all natural surfaces may require excessive cutting, reducing the final carat weight of the polished diamond.
Preserving Crystal Integrity

Some rough diamonds have growth lines or inclusions that, if cut away, could weaken the stone or impact its durability. Leaving a natural in a strategic area helps maintain the diamond’s overall strength.
Minimizing Waste

Since natural diamonds are rare and valuable, preserving part of the rough minimizes unnecessary loss of material during cutting.
Proof of Natural Origin

In some cases, gemologists and collectors appreciate naturals as evidence that the diamond was cut from a genuine rough stone rather than being lab-grown or heavily altered.
Impact on a Diamond’s Appearance and Quality
Polish Grade:

Naturals are considered minor surface features and are factored into the polish grade of a diamond. A diamond with significant naturals may receive a lower polish grade from gemological laboratories like DCLA, GIA, or AGS.
Location Matters:

If confined to the girdle area, naturals do not significantly affect the diamond’s overall appearance, brilliance, or value.
If present on the crown or table (top facets), they may be more visible and could impact the diamond’s aesthetic appeal.
Girdle Thickness Considerations:

Some naturals can contribute to an uneven girdle thickness, which might affect durability. A very thin girdle with a natural could increase the risk of chipping.
How to Identify a Natural in a Diamond?
Visible under Magnification
Naturals are typically small, textured, and may appear frosty or grainy under a jeweler’s loupe (10x magnification) or a microscope.
GIA & DCLA Reports
If a diamond has a natural, it is often noted in the grading report, usually under the clarity characteristics or polish comments section.
Naturals vs. Other Surface Features
Natural vs. Extra Facet:
A natural is an original rough diamond surface left untouched, while an extra facet is a man-made additional cut that is not part of the standard faceting pattern.
Natural vs. Cavity:
A natural is a minor surface remnant, whereas a cavity is an indentation or deeper surface flaw that can affect durability.
Are Naturals a Flaw?
Not necessarily. If located on the girdle, naturals are generally not a concern for beauty or durability. They do not impact the diamond’s brilliance or fire, and they are considered an acceptable feature in diamond cutting, especially for maximizing weight retention.

However, if a natural extends beyond the girdle onto visible facets, it could slightly affect the stone’s appearance and might be more noticeable.

A natural diamond is a gemstone composed of crystallized carbon that was formed deep within the Earth’s mantle under extreme heat and pressure over 1 to 3 billion years ago. Unlike lab-grown diamonds, which are created in controlled environments, natural diamonds are mined from the Earth and are considered one of the rarest and most valuable gemstones.

Formation of Natural Diamonds
Natural diamonds form 100–200 km (62–124 miles) below the Earth’s surface, where intense pressure (725,000+ psi) and high temperatures (1,100–1,400°C) cause carbon atoms to bond in a unique cubic crystal structure. These diamonds are then transported to the surface through volcanic eruptions, specifically via kimberlite pipes—ancient volcanic conduits that carry rough diamonds upward.

Characteristics of Natural Diamonds
Composition:
Made of pure carbon arranged in a tetrahedral lattice, giving diamonds their exceptional hardness.
Hardness (Mohs Scale 10):
The hardest known natural material, making it highly resistant to scratches and wear.
Brilliance & Fire:
Due to its high refractive index (2.42), a well-cut diamond reflects and disperses light, creating its signature sparkle.
Unique Inclusions & Imperfections:
Most natural diamonds contain inclusions (internal characteristics) and blemishes (surface characteristics) that serve as fingerprints of their natural origin.
Rarity & Value:
Large, flawless natural diamonds are exceptionally rare, making them highly valuable compared to lab-grown alternatives.
Types of Natural Diamonds
1. White (Colorless) Diamonds
The most sought-after diamonds, graded on a color scale from D (colorless) to Z (light yellow or brown).
The less color, the higher the value.
2. Fancy Color Diamonds
Natural diamonds can exhibit blue, pink, yellow, green, orange, and even red hues due to trace elements or structural irregularities.
Examples:
Blue diamonds (trace boron) – Example: The Hope Diamond
Pink diamonds (structural distortions) – Example: Argyle Pink Diamonds
Yellow diamonds (trace nitrogen) – Example: Tiffany Yellow Diamond
3. Industrial Diamonds
Low-quality natural diamonds used in cutting, drilling, grinding, and polishing tools due to their extreme hardness.
How Natural Diamonds Are Mined
Natural diamonds are extracted from the Earth using various mining techniques:

Kimberlite Pipe Mining (Primary Source)

Diamonds are found in kimberlite pipes, ancient volcanic conduits rich in diamond-bearing rock.
Mined using open-pit or underground methods.
Alluvial Mining (Secondary Source)

Diamonds eroded from kimberlite pipes are transported by rivers and accumulate in riverbeds or coastal areas.
Marine Mining

Specialized ships mine diamonds from the ocean floor, particularly off the coast of Namibia and South Africa.
How Natural Diamonds Are Identified
To distinguish a natural diamond from a lab-grown or synthetic diamond, experts use advanced testing and certification from recognized gemological labs like DCLA, GIA, and AGS.

Key Identification Methods:
Inclusions & Growth Patterns: Natural diamonds contain unique inclusions, such as tiny crystals, feathers, or graining patterns, absent in lab-grown diamonds.
Fluorescence & Phosphorescence: Some natural diamonds exhibit fluorescence under UV light, while lab-grown diamonds may show different reactions.
Spectroscopy & Advanced Testing: High-tech tools like FTIR (Fourier-transform infrared spectroscopy) and UV-Vis spectrometry help differentiate natural diamonds from synthetic or treated ones.
Natural Diamonds vs. Lab-Grown Diamonds
Feature Natural Diamond Lab-Grown Diamond
Formation Formed over billions of years in Earth’s mantle Created in weeks using HPHT or CVD methods
Origin Mined from the Earth Manufactured in a lab
Inclusions Natural growth patterns and inclusions Different internal characteristics, sometimes with metallic inclusions (HPHT)
Rarity Extremely rare, especially high-quality stones Mass-produced
Price Higher due to rarity Generally 50–70% cheaper
Resale Value Strong resale and investment value Limited resale market
Ethical Concerns Some concerns over ethical sourcing (unless from certified conflict-free sources) Considered conflict-free and more sustainable
Ethical & Sustainable Sourcing of Natural Diamonds
Concerns over “blood diamonds” (conflict diamonds) led to the Kimberley Process Certification Scheme (KPCS), which ensures that natural diamonds are ethically sourced and do not fund conflicts.

Reputable diamond companies, including DCLA-certified brands, focus on:

Conflict-free mining practices
Fair labor policies
Sustainable environmental impact reduction
Why Choose a Natural Diamond?
Timeless Value: Unlike lab-grown diamonds, natural diamonds retain strong resale and investment value.
Unique & One-of-a-Kind: Each natural diamond has its own history, inclusions, and growth patterns, making it a unique creation of nature.
Symbolism & Tradition: Used in engagement rings, heirlooms, and high jewelry, natural diamonds carry deep emotional and historical significance.

A needle inclusion is a type of internal characteristic found in natural diamonds. It appears as a long, thin, needle-like crystal trapped inside the diamond during its formation. These inclusions are often transparent or white, but they can also appear in shades of black, brown, or other colors, depending on the type of mineral present.

How Needle Inclusions Form
Natural diamonds form over billions of years deep within the Earth’s mantle under extreme pressure and heat. During this process, various mineral deposits, gases, or even other diamond crystals can become trapped inside the growing diamond. When these inclusions form in an elongated shape, they are classified as needle inclusions.

Composition: Needle inclusions can be made of other minerals (such as garnet, olivine, or pyroxene) or even diamond itself.
Growth Influence: The presence of a needle inclusion can sometimes indicate the diamond’s growth pattern and conditions within the Earth.
Appearance of Needle Inclusions
Shape: Thin, elongated, needle-like structure
Color: Usually transparent or white, but can also be black, brown, or yellow depending on the trapped material
Size: Ranges from microscopic (only visible under magnification) to larger inclusions that may affect transparency
Position: Found anywhere in the diamond, including near the surface, within the pavilion, or in the crown
Impact of Needle Inclusions on Diamond Quality
1. Clarity Grade
Needle inclusions affect a diamond’s clarity grade, which is assessed by laboratories like DCLA, GIA, and AGS.

If the needle is small and not visible to the naked eye, it may have minimal impact on the clarity grade.
If the needle is large, numerous, or positioned in a way that affects transparency, it may lower the diamond’s clarity rating significantly.
2. Visibility in Jewelry
Small needles in the pavilion (bottom of the diamond): Often not noticeable and have little impact on beauty.
Larger needles near the table (top flat facet): May be more visible and slightly reduce brilliance.
Clusters of needle inclusions: When multiple needles form in the same area, they can create a hazy or cloudy effect, reducing the diamond’s overall brightness.
3. Structural Integrity
Unlike surface-reaching inclusions (such as feathers or cavities), needle inclusions do not typically weaken a diamond’s durability.
However, if located near the girdle or in a region of high stress, a large needle inclusion might slightly affect the diamond’s strength.
How to Identify Needle Inclusions
1. Under Magnification
Needles are difficult to spot with the naked eye but can be seen under a 10x jeweler’s loupe or a microscope. They often appear as thin, hair-like lines inside the diamond.

2. Diamond Grading Reports
Professional reports from DCLA, GIA, or AGS will note needle inclusions under clarity characteristics.
Needles are often indicated on a diamond’s plot diagram, showing their location and size.
3. Using Fluorescence & Light Scattering
Some needles become more visible under UV light.
Strong lighting may make them appear as tiny bright or dark streaks inside the diamond.
Needle Inclusions vs. Other Inclusions
Inclusion Type Description Impact on Clarity
Needle Thin, elongated crystal trapped inside the diamond Minimal unless large or clustered
Pinpoint Tiny, dot-like crystal Very minor effect
Cloud Group of tiny pinpoints, creating a hazy look Can lower brilliance if dense
Feather Small crack or fracture May impact durability
Crystal Distinct mineral inclusion, often shaped like a small crystal Can be noticeable if dark
Are Needle Inclusions a Dealbreaker?
Not necessarily.

If small and not visible to the naked eye, needle inclusions have little impact on beauty or value.
If multiple needles cluster together, they might create a cloudy effect, reducing transparency and brilliance.
Always review a diamond’s clarity in person or with a magnification tool to determine if the needle inclusion affects its overall appearance.

A nick is a small surface blemish found on a diamond, typically appearing as a tiny break or indentation along the girdle or facet junctions. It is too small to be classified as a chip, but it can still impact the diamond’s polish grade and overall appearance. Nicks often occur due to accidental impact, improper handling, or wear over time.

Characteristics of a Nick
Size: Small, shallow indentation (smaller than a chip)
Location: Most commonly found on the girdle, but can also occur on facet edges
Appearance: Can look like a tiny white mark, scratch, or indentation under magnification
Cause: Often results from mechanical wear, accidental bumps, or improper handling during cutting, setting, or daily wear
Impact of a Nick on a Diamond’s Quality
1. Polish Grade
A nick affects the polish grade of a diamond, as it disrupts the smoothness of the surface.
If minor, it may not significantly lower the diamond’s overall grade, but if noticeable, it can result in a lower polish rating on a grading report from DCLA, GIA, or AGS.
2. Visibility & Aesthetic Impact
Small nicks on the girdle: Often invisible to the naked eye and do not affect brilliance.
Larger nicks on facet edges: Can slightly affect light performance, especially if they disrupt the diamond’s symmetry.
3. Durability & Wear Resistance
A single, shallow nick usually does not impact a diamond’s structural integrity.
However, multiple or deep nicks along the girdle may make the diamond more susceptible to chipping over time, especially if the girdle is very thin.
Nick vs. Other Diamond Blemishes
Blemish Type Description Impact on Diamond
Nick Small, shallow indentation on the girdle or facet edge Minor, affects polish but not durability
Chip Larger, more visible break in the diamond, often near the girdle or culet Can weaken durability and lower value
Scratch A fine line on the diamond’s surface Affects polish but can often be removed
Abrasion Small, worn-down facet edges from prolonged wear Reduces brilliance and can make the diamond look dull
Can a Nick Be Repaired?
Polishing/Recutting: A minor nick can sometimes be polished out by a professional jeweler. However, this may slightly reduce the diamond’s carat weight.
Re-setting: If the nick is on the girdle and affects durability, the diamond can be set in a way that protects the weak spot (e.g., a bezel setting).