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Diamond Guide

This guide explores how to assess diamond grades according to the industry standards in cut, color, clarity, and carat.
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What are diamonds?

Diamonds, often seen as symbols of eternal love and commitment, are the most cherished and heavily marketed gemstones globally.

Their exceptional beauty, brilliance, and durability have captivated people for centuries, making them a cornerstone of the jewelry industry. The word “diamond” itself comes from the Greek word “adamas,” meaning indestructible, reflecting their remarkable hardness and enduring allure.

The Nature of Diamonds

The Atomic Structure

Both diamonds and graphite are composed of carbon, yet their atomic structures differ significantly. In diamonds, each carbon atom bonds with four others, forming a robust and transparent structure. In contrast, graphite’s carbon atoms bond with only three others, creating a soft, opaque material. This structural difference gives diamonds their unmatched hardness and transparency, while graphite remains soft and dark.

Formation of Diamonds

Diamonds form under extreme conditions of high pressure and temperature, approximately 200 kilometers below the Earth’s surface. Here, carbon atoms are tightly compressed, bonding into a crystalline structure. This requires pressures 50,000 times greater than at the Earth’s surface and temperatures around 1600°C.

The Journey to the Surface

Kimberlite Pipes

Diamonds are brought to the Earth’s surface by volcanic eruptions through unique volcanoes known as kimberlites. These eruptions occur when deep-seated gas heats up and expands, carrying diamonds and other rocks to the surface. Although diamonds formed billions of years ago, it takes millions of years for them to reach the surface, making kimberlite eruptions rare. The most recent such eruption occurred 13 million years ago.

Laboratory-Grown Diamonds

Today, scientists can create diamonds in laboratories by replicating the natural conditions required for their formation. These lab-grown diamonds possess the same physical and chemical properties as natural diamonds.

Global Distribution and Mining

Historical Sources

For over a thousand years, starting from the 4th century BC, India was the world’s only source of diamonds. Significant discoveries in Brazil in 1725 and in South Africa in the 1870s dramatically increased the global diamond supply. Currently, diamonds are mined in about 25 countries, including several African nations, Russia, and Australia.

Primary and Secondary Deposits

Diamonds are found in primary deposits, such as kimberlite and lamproite pipes, and secondary deposits formed through erosion. These secondary deposits include river channels and coastal areas where diamonds have been transported by water.

Notable Diamond Sources

South Africa

Diamonds were first discovered on the shores of the Orange River. After a series of diamond rushes and turbulent ownership changes, nearly all the deposits came under the control of De Beers Consolidated Mines, Ltd. by 1888. South African diamonds are among the world’s most famous, with mines such as Premier, Jagersfontein, Bultfontein, Dutoitspan, and Wesselton being particularly renowned. While South Africa remains a leading diamond producer, large stones are becoming scarce.

India

Historically, India was the first major source of diamonds, producing many famous gems, including the Hope Diamond. Mines are located in Golconda, Andhra Pradesh, Kollur, and other areas. Indian diamonds are primarily found in alluvial deposits, sandstone, and gravel beds.

Brazil

Brazil produces a large quantity of diamonds, though most are not of gem quality. The Diamantina district, opened in 1725, along with Bahia, Minas Gerais, and other states, are key sources. Brazilian diamonds occur in various rock types and alluvial deposits, with occasional large gemstones found. Bahia is known for black microcrystalline diamond, or carbonado.

Borneo and Indonesia

These regions have small alluvial deposits, producing mostly small diamonds. Borneo’s diamonds are noted for being particularly hard.

Venezuela

Venezuela has significant alluvial diamond production, mainly consisting of small, yellowish crystals.

Russia

One of the world’s leading diamond producers, Russia has several hundred pipes, mainly in Siberia. While Russian diamonds are typically small, they are of good color and transparency. The “Mir” pipe is among the most famous, despite the challenging mining conditions.

Australia

Northwestern Australia’s geology is similar to South Africa’s diamond regions. Significant discoveries include the AK-1 pipe, found in 1979, which contains high-grade kimberlite. Although Australian diamonds tend to be small and low in quality, the country is expected to become the world’s largest producer by volume.

United States

The only significant North American deposit is at Murfreesboro, Arkansas. This large pipe, located on government land, is primarily mined by tourists. Large alluvial diamonds have also been found across the United States, likely carried south by glaciers. Notable finds include the “Dewey” and “Punch Jones” diamonds in Virginia.

Other African Countries

  • Zimbabwe: Known for alluvial deposits.
  • Angola: Produces fine stones, though political issues have interrupted production.
  • Ghana: Produces industrial-grade diamonds from gravel beds, with some gem-quality stones.
  • Ivory Coast and Republic of Guinea: Known for alluvial diamonds.
  • Namibia: Large deposits near the Atlantic coast worked by massive machinery.
  • Central African Republic: Diamonds found in gravel beds.
  • Zaire and Sierra Leone: Alluvial diamonds, with Sierra Leone producing some of the world’s finest.
  • Tanzania: Contains a large pipe discovered by John Williamson in 1935.
  • Lesotho and Botswana: Also significant diamond sources.

The Unique Properties of Diamonds

Crystal Structure

Diamonds typically form in an octahedral shape, though they can also appear as cubes or dodecahedra. These shapes are highly symmetrical, reflecting the cubic crystal system of diamond formation. Some diamonds also form as twins, known as macles, or with etched, rounded surfaces.

Hardness and Durability

Diamonds are the hardest natural substance, capable of scratching all other materials. This extreme hardness is measured using the Mohs scale, where diamonds rank at the top with a hardness of 10. However, diamonds are also brittle and can shatter if struck with sufficient force.

Surface and Density

Diamonds repel water and attract grease, a property utilized in mining to separate them from other minerals. They have a specific gravity of 3.52, meaning they are 3.52 times denser than water.

Optical Properties

Diamonds are prized for their brilliance and luster, resulting from their high refractive index and dispersion. These properties cause light to bend and split into a spectrum of colors, creating a glittering effect. The refractive index of diamonds is 2.419, one of the highest of any transparent material.

Thermal and Electrical Conductivity

While diamonds are poor electrical conductors, certain types, like Type IIb blue diamonds, can conduct electricity due to boron impurities. Diamonds excel in thermal conductivity, outperforming materials like copper, making them valuable in industrial applications for cooling electronic components.

The 4 C’s of a Diamond

The 4C’s play an integral role in reflecting the characteristics of the diamond. The Gemological Institute of America (known as GIA) is an international diamond grading system that serves as a universal benchmark for evaluating diamonds worldwide, providing buyers with a comprehensive understanding of their diamond’s attributes. This foundation assesses four key characteristics: color,cut, clarity, and carat, all of which are clearly reflected on the GIA diamond grading chart.

Lab-grown diamonds, being genuine diamonds, undergo the same rigorous evaluation process as natural diamonds according to the GIA’s established standards. These parameters remain consistent for both lab-grown and mined diamonds.

It’s imperative to highlight that lab-grown diamonds are indistinguishable from mined diamonds in terms of their optical, physical, and chemical properties. Consequently, reputable independent gemological organizations officially grade the quality of lab-grown diamonds using the same 4Cs framework. Just like their natural counterparts, lab-grown diamonds exhibit variations in their 4C grades, spanning from poor to excellent quality.

Cut

The craftsmanship behind a diamond’s cut profoundly impacts its quality, characterized by its symmetry and proportions. Achieving a superior cut demands the expertise of a highly skilled and experienced artisan.
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Fair

Good quality cut which reflects some light while maximizing weight. While not as brilliant as a good cut, still a quality diamond.

Good

Premium quality cut to optimize the size without sacrificing quality or beauty. Reflects most light that enters.

Very Good

Superior quality cut that reflects nearly as much light as the ideal cut while at a substantially lower cost.

Ideal

Exquisite quality cut to create the optimal combination of brilliance and fire. Reflects nearly all light that enters the diamond.

Super Ideal

Cut to the most exacting standards. These diamonds have the most desirable dimensions and are proportioned to return the maximum possible light.

J Color

J color diamonds look mostly colorless to the naked eye, but usually have a faint yellow tint that’s easy to notice under bright lights and magnification.

I Color

Near-colorless. Slightly detected color—a good value.

H Color

Near-colorless. Color noticeable when compared to diamonds of better grades, but offers excellent value.

G Color

Near-colorless. Color noticeable when compared to diamonds of better grades, but offers excellent value.

F Color

Colorless. Slight color detected by an expert gemologist, but still considered a “colorless” grade—a high-quality diamond.

E Color

Colorless. Only miniscule traces of color can be detected by an expert gemologist—a rare, high quality diamond.

D Color

Colorless. Slight color detected by an expert gemologist, but still considered a “colorless” grade—a high-quality diamond.

Color

There is always a misconception that diamonds are always perfectly transparent. Nonetheless, with the presence of trace elements within diamonds, they can display subtle hues.
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Clarity

Clarity references the absence of internal inclusions and surface blemishes on a diamond. The scale ranges from Internally Flawless to Included.
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Slightly included 2. Inclusions are visible under 10x magnification and may be visible with an unaided eye. More inclusions than SI1.

Slightly included 1. Inclusions are visible under 10x magnification, but may not be very visible with an unaided eye.

Very slightly included 2. Difficult to see inclusions under 10x magnification. Typically cannot see inclusions with the naked eye. Slightly more inclusions than VS1.

Very slightly included 1. Difficult to see inclusions under 10x magnification. Typically cannot see inclusions with the naked eye.

Very very slightly included 2. Very difficult to see under 10x magnification. Slightly more inclusions than VVS1.

Very very slightly included 1. Very difficult to see under 10x magnification.

Internally Flawless. No internal flaws.

Flawless with no internal or external flaws. Extremely rare and valuable.

Carat

A carat is a unit of weight used specifically to measure diamonds and other gemstones. It is often mistaken for a measurement of size, but a carat is actually a measure of how much a gemstone weighs.
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