Have you ever held a diamond and wondered how something so clear and hard formed miles beneath the surface? Natural diamonds begin as carbon atoms crushed by extreme pressure and heat in the mantle, then travel to the surface through volcanic kimberlite pipes or wash into riverbeds as alluvial deposits.
You will also learn how grown diamonds are made, so you can compare natural formation with lab methods like high-pressure high-temperature and chemical vapor deposition, and better appreciate their rarity and beauty. Expect clear explanations of the crystal lattice, geological time, and why some gems are found in one place and not another.
If you want real examples and friendly answers, PriceScope, the largest diamond and jewelry forum, connects you with collectors, gemologists, and jewelers who explain formation, grading, and sourcing in straightforward terms.
A natural diamond is a precious gemstone formed deep within the Earth’s mantle over billions of years. It starts as pure carbon atoms subjected to intense heat and pressure, causing the atoms to bond in a unique cubic crystal lattice structure. This arrangement is what makes diamonds the hardest known natural material on Earth.
Each carbon atom in a diamond is bonded to four others, creating a robust network. This structure gives diamonds remarkable hardness, brilliance, and durability. They also have very high thermal conductivity and exceptional transparency, resisting heat and chemicals better than most materials.
Diamonds come in various colors, from the well-known colorless variety to rare hues like blue, yellow, green, pink, and even red. These colors are usually due to tiny impurities or structural irregularities within the stone. The natural process of diamond formation spans one to three billion years, making each diamond unique with distinct growth patterns and inclusions that tell its geological story.
The intense pressure and temperature where diamonds form (roughly 140 to 190 kilometers below Earth’s surface) result in their remarkable physical properties. Volcanic eruptions or other geological activities later bring these diamonds to the surface, where they can be mined.
How do experts identify a natural diamond? They examine inclusions, growth patterns, nitrogen chemistry, isotopic ratios, and strain patterns under microscopes and spectrometers. Lab-grown diamonds often show metallic flux, unusual inclusions, or growth features tied to high-pressure, high-temperature, or chemical vapor deposition methods, which differ from natural mantle signatures. Would you like to see examples of how these tests look under the microscope?
Diamonds are formed through remarkable natural processes under extreme conditions, with four known formation methods recognized by scientists. While each technique is unique, most natural diamonds come from a specific geological process deep within the Earth.
The majority of natural diamonds originate more than 120 kilometers (about 75 miles) beneath the Earth’s surface in the mantle. Here, immense heat ranging from 900°C to 1300°C and pressures exceeding 45 kilobars exist. Over millions to billions of years, these harsh conditions cause carbon atoms to crystallize into diamonds. This process requires a carbon source in a fluid or molten state within the mantle that is sufficiently reduced to prevent oxygen from binding with carbon, enabling diamond crystal growth.
Once formed, diamonds must be transported to the surface. This happens when parts of the mantle partially melt, generating magma that rapidly ascends via volcanic eruptions. As this magma cools, it solidifies into kimberlite rock, typically in vertical formations called kimberlite pipes. These pipes carry diamonds from deep underground closer to the Earth’s surface and represent the principal source of natural diamonds worldwide. Yet only about 1% of known kimberlite pipes contain economically valuable diamond deposits, underscoring the rarity of gem-quality stones.
Diamonds can also form or be transported by tectonic processes associated with plate movements. Some small diamonds have been discovered in ultra-high-pressure metamorphic rocks in places like Kazakhstan and Norway. These diamonds are believed to rise to the surface through mountain-building movements of tectonic plates.
Another related process is subduction, where one tectonic plate descends below another and sinks into the mantle. This journey recycles organic carbon back into the mantle, where it can crystallize into diamonds along with other mantle materials. Some diamonds even show elemental signatures indicating they formed at depths exceeding the upper mantle boundary, highlighting their complex origins tied to deep Earth cycles and tectonic dynamics.
Diamonds can form as a result of meteorite impacts on Earth. When large meteorites collide with the surface, the shock creates extreme pressure and heat suitable for diamond formation. Diamonds found near impact craters, such as the Popigai crater in Siberia, are usually tiny and of lower quality. The conditions generated by these impacts achieve the rapid pressure and temperature changes necessary to transform carbon into tiny diamond crystals.
Beyond Earth, nanodiamonds (extremely tiny diamonds only a few billionths of a meter across) have been found around newly formed stars and within meteorites. Though too small for practical use, these nanodiamonds are essential for understanding cosmic processes and the materials that make up our galaxy. Their presence suggests that diamond formation is not unique to Earth but a widespread phenomenon in the universe.
Before diamonds are cut and polished into the sparkling gems seen in jewellery stores, they exist as rough crystals formed deep within the Earth. These rough diamonds have a glassy shine and can display subtle tones of yellow, brown, or grey. Their shapes are determined by the arrangement of carbon atoms in a rigid cubic lattice.
Natural diamonds begin their existence as unpolished crystals deep within the Earth’s mantle. At depths between 150 and 250 kilometers, extreme heat and pressure cause carbon atoms to bond in a concrete cubic lattice structure. This gives rise to the diamond’s crystal form, often an octahedron shape resembling two pyramids joined at the base. Other common shapes include cubes and dodecahedra, twelve-sided crystals with curved faces.
While still embedded in volcanic rock called kimberlite, rough diamonds show a glassy, sometimes slightly colored sheen. Their edges can appear sharp or softened, with some crystals exhibiting etching, which reveals the harsh, changing environments they endured during formation. These features, such as resorption, where parts of the crystal surface are dissolved, tell the story of their journey from deep underground to the Earth’s surface.
The process takes place over a vast timescale, commonly spanning one to three billion years. During this time, carbon atoms realign into the crystal lattice under temperatures of about 900°C to 1300°C and pressures around 45,000 times atmospheric pressure. Occasionally, impurities like nitrogen or boron integrate into the lattice, influencing coloration and clarity. When volcanic eruptions push magma rapidly upwards through kimberlite pipes, diamonds are transported to the surface, preserving their raw crystal form, waiting to be polished.
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Diamonds are primarily mined from kimberlite and lamproite pipes. These are volcanic formations that bring diamonds from deep within the Earth’s mantle to the surface. When a diamond-bearing pipe is located, large-scale mining operations use heavy machinery and advanced technology to extract the diamond-rich rock.
In addition to primary sources, diamonds are also found in alluvial deposits. These occur where rivers and erosion transport diamonds away from their original volcanic source and deposit them in gravel beds. These alluvial deposits can often be mined using simpler methods, sometimes even by artisanal miners.
Historically, India was the first known source of diamonds, mainly from alluvial deposits. In the late 19th century, significant discoveries occurred in South Africa near Kimberley. This led to the rise of large mines and companies like De Beers, which once controlled a substantial share of global diamond production.
Today, the world’s leading diamond producers include Russia, Botswana, Canada, Australia, and several African countries like Angola and South Africa. Russia’s mines in the Yakutia region, such as Udachny and Mir, are among the largest. Botswana’s Orapa and Jwaneng mines are also top producers. Canada’s Ekati and Gahcho Kué mines add to significant global output, and Australia’s Argyle mine was well known for its pink diamonds before its recent closure.
Diamonds have been found in numerous countries worldwide, including the United States (notably Arkansas), but commercial mining is mainly active in a handful of countries with economically viable deposits.
Cutters begin by studying the rough stone under magnification and with 3D imaging software. They model internal inclusions, crystal orientation, and extreme variations in clarity to select a shape that maximizes carat weight while enhancing light return. For lab-grown diamonds, which share the same crystal structure as stones formed deep in the mantle under high pressure and high temperature, the planning step looks identical and uses the same scans and algorithms to predict yield.
Natural diamonds often have cleavage planes, lines along which the crystal will split cleanly. Cutters use these planes to cleave a stone with a precise blow or to orient a saw. When no safe cleavage plane exists, they use a diamond-tipped saw or a laser to cut through the lattice. Lasers vaporize material with minimal vibration, which helps when an inclusion sits near the intended split.
Bruting gives the stone its basic outline. For a round brilliant, the cutter grinds two diamonds against each other on a spinning lathe to create a true round girdle. For fancy shapes—oval, emerald, cushion—bruting uses abrasive wheels and controlled motion to build the desired silhouette while keeping symmetry and maximum carat retention.
Before final facets are laid down, cutters often pre-form the stone with laser sawing and automated grinding. Laser pre-forming can remove a section around a stubborn inclusion or create fine cuts for fancy shapes. Computer-assisted design and machine control let cutters index facets precisely so the final stage starts from a stable, predictable blank.
Polishing transforms planes into precise facets that reflect and refract light. Cutters mount the stone on a dop stick, set it against a rotating scaife charged with diamond powder, and polish each facet according to exact angles. The angle and placement of each table, kite, and star facet determine how light refracts through the crystal lattice and returns to the eye as sparkle and fire.
A stone’s crown height, pavilion depth, and table size control light performance. If the pavilion is too deep, light leaks out the sides. If the table is too large, you lose dispersion. Tools that simulate light paths let cutters aim for optical targets that maximize brilliance, scintillation, and color performance in the stone.
After polishing, cutters inspect the symmetry of facet alignment and the quality of each polished surface. Tiny polishing lines or off-axis facets reduce performance and lower grade. Labs assess these attributes alongside clarity and color to produce a report that tells how the cut will present to the observer.
Computer-assisted design and robotic polishing speed repeatable cuts and reduce waste. Robots can index a stone to within tiny tolerances and apply consistent pressure during polishing. Laser etching marks a stone with ID numbers and can also remove inclusions selectively before traditional polishing. These tools complement hand skills rather than replace them.
Fancy cuts like the emerald, asscher, and heart require different polishing sequences and a higher degree of human judgment. Cutters balance optical goals against the crystal’s natural growth direction and any internal features. Clients can request custom proportions to emphasize color or size, which changes how facets are arranged and how light behaves inside the diamond.
Diamonds are priced primarily based on the well-known 4Cs (Cut, Color, Clarity, and Carat weight). These four characteristics combine to determine a diamond’s quality and market value.
Carat measures the diamond’s weight, with one carat equaling 0.2 grams. Larger diamonds become exponentially more expensive because bigger stones are much rarer than smaller ones. For example, a 2-carat diamond can cost more than twice as much as a 1-carat diamond of similar quality due to its scarcity. Slight differences in carat weight around pricing thresholds can also cause significant price jumps.
Cut quality affects how well a diamond reflects light, influencing its sparkle and brilliance. A superior cut grade generally commands a higher price because it enhances the diamond’s overall beauty, regardless of size.
Color is graded on a scale from D (colorless) to Z (light yellow or brown tint). Diamonds closer to colorless tend to be more valuable. However, near-colorless grades like G or H offer a good balance of appearance and value, appearing nearly white but costing less than the highest color grades.
Clarity assesses how free a diamond is from internal flaws or blemishes. While flawless diamonds are exceedingly rare and costly, most inclusions are microscopic and have minimal effect on beauty, allowing buyers to save by opting for slightly lower clarity grades.
Besides the 4Cs, diamonds with fancy colors such as pink, blue, green, or yellow are valued differently. These fancy colored diamonds are much rarer and can be extremely expensive due to their unique hues and scarcity.
Buying a diamond is an exceptional experience. When you visit us at PriceScope, we’ll talk about what’s most important to you (size, sparkle, or budget), and walk you through each diamond’s qualities so you feel confident and informed.
Join thousands of engaged buyers, enthusiasts, and industry experts at PriceScope who rely on our unbiased forums, advanced tools like the Holloway Cut Advisor, and carefully vetted vendor partnerships with trusted retailers like Whiteflash, James Allen, and Blue Nile — we host the largest diamond and jewelry forum and practical guides that help sellers set realistic expectations and get better offers. Start your diamond education journey today with our comprehensive guides, pricing insights, and sales pressure-free community support, because when it comes to diamonds, knowledge is your most valuable investment.
Join thousands of engaged buyers, enthusiasts, and industry experts at PriceScope who rely on our unbiased forums, advanced tools like the Holloway Cut Advisor, and carefully vetted vendor partnerships with trusted retailers like Whiteflash, James Allen, and Blue Nile. Use our comprehensive guides, pricing insights, and sales pressure-free community support to build the confidence you need before you buy. Ready to ask a question in our forums or run your next stone through the Holloway Cut Advisor?
Compare certificates and look for a reputable lab report that lists the origin. View multiple images and videos, and request a table view and a plot of inclusions if available. Use PriceScope forums to read buyer experiences and vendor feedback on retailers like Whiteflash, James Allen, and Blue Nile. Check return policies, warranties, and whether the girdle is laser inscribed with a report number. Will you use the Holloway Cut Advisor to evaluate cut quality before you commit?
How hard are they compared to mined diamonds? Identical in hardness when the crystal structure is intact. Can they be resold? The secondary market is evolving, with prices differing from those of natural stones; therefore, it’s advisable to compare offers. Do lab-grown diamonds maintain value? Market dynamics and consumer preference shape resale value. What about heirloom use? A lab-grown diamond can become an heirloom if you treat it like one and document its origin and grading. Which question should you ask your jeweler first? Ask for the grading report and origin disclosure before you view the stone.
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