DIAMOND

Name: Diamond (from the Greek adamas, "unbreakable")

Symbol: C

Group: 14

Period: 2

Block: p

Category: Nonmetal (crystalline allotrope of carbon)

Atomic number: 6

Atomic mass: 12.011 u

Electrons per shell: 2.4

Electronegativity: 2.55

Density: 3.52 g/cm³

Melting point: Not defined (sublimes or transforms into graphite at 3,550 °C in an inert atmosphere)

Boiling point: Not applicable (sublimes at high temperatures)

Thermal conductivity: 2,000–2,500 W/(m·K) (one of the highest among solids)

Electrical conductivity: ~10⁻¹⁵ S/m (electrical insulator)

Magnetic order: Diamagnetic

Ordinary state: Solid

Oxidation states: 0 (mainly), +2, +4 (in compounds)

Mohs hardness: 10 (the hardest known natural material)

Vickers hardness: ~10,000 MPa

Brinell hardness: Non-standard (extreme hardness makes measurement difficult)

Most stable isotopes: C-12 (98.93%), C-13 (1.07%)

Discoverer: Not attributed to a specific individual; known since ancient times (3000 BC, India), scientifically characterized in the 18th century

Diamond is the crystalline form of carbon that forms from traces of the element subjected to extreme temperatures and pressures. How is it formed?

To understand how diamonds form, keep in mind that carbon, thanks to many of its characteristics, such as its small atomic radius and its ability to bond with itself billions of times to form perfectly symmetrical structures, is one of the few elements capable of contracting in such a way that it can "reconcentrate" into smaller volumes with the same number of atoms. Let me explain:

Imagine you have one hundred ping-pong balls in a relatively large box, and suddenly, it begins to contract more and more, so that the balls have to squeeze more and more tightly as the space is reduced to the point where they form a compact block or "pineapple." In other words, the box, or rather, the volume of the container, has been reduced, but the number of ping-pong balls remains the same.

Something similar happens with diamonds, which are, after all, compact forms of carbon. The reason they suffer this concentration or "crowding" is due to pressure, which pushes the atoms against each other, while temperature facilitates their movement and prior dislocation before they re-arrange themselves in what we know as a new "crystalline structure," which allows them to fit more atoms into smaller spaces. This is why diamond is almost twice as dense as graphite, because it contains more mass per volume. A consequence of this contraction and subjection to similar conditions is the absence of other light elements such as boron or beryllium, which "fall out" during the crystallization process, giving diamond its classic transparent, crystalline appearance. The entire process of dislocation, contraction, and regrouping of atoms is only possible at lower levels of the Earth's mantle, so by now you're probably wondering how we can possibly find them on the surface (note that even the deepest mines are still considered part of the surface). The answer is that diamonds are dragged to the surface by magmatic movements. This is why the amount of diamonds that, for better or worse (personally, it doesn't matter to me), we will never access are found in the lower layers of the Earth, where they will remain for the rest of time.

When diamond is chemically pure, we are looking at elemental carbon in crystalline form. In this sense, it resembles graphite, although the similarities end there, as diamond is quite different from the former in virtually all its properties.

Diamond, in its purest form, is transparent and vitreous. It has some of the highest properties of all natural or synthetic materials, among which its legendary hardness stands out. Now, we are faced with what has been, for decades (perhaps centuries), a huge misunderstanding regarding what we normally understand by "hardness."

The "hardness" of a diamond refers to its unmatched resistance to abrasion. This means that nothing can scratch a diamond, except, obviously, another diamond (we will see later that there are exceptions). The misunderstanding regarding what is actually defined as hardness in this context is similar to that of "stainless" steel, with poor translations leading to confusion.

The English refer to hardness as "hardness," but they differentiate it from "toughness." They are completely different properties, but since both they and we say something is "hard" when it is "strong," it is to be expected that such errors arise, as I mentioned before.

A diamond is hard from the perspective of a jeweler, a gemologist, and more broadly (given their greater repertoire and depth of knowledge) a geologist. The famous "hardness of diamonds" is nothing more than their resistance to abrasion. In other words, there is no solid element or compound capable of wearing down diamonds, the queen of gems, not only because of this characteristic, but also because of many others, as we will see later.

I say this and insist on this again and again because I see that whenever TV or any other type of media talks about diamond hardness, it is directly or indirectly implied that diamonds are "indestructible"… far from it.

It's true that diamond's toughness is greater than that of other more abundant and well-known minerals, such as quartz (SiO2), but it is still a crystalline form of a chemical element and therefore behaves as such. Its toughness, although better than most natural and synthetic crystals, is far, far inferior to common grades of steel, for example. Consider how "destructible" diamond is, in fact, pulverized with a regular hammer. What I want you to understand, and this is the last time I'll repeat it, is that diamond's hardness does not mean that it is resistant to impact or stress, but rather to wear.

As if the "problem" weren't enough, there are no clear etymologies to distinguish resistance to abrasion wear (the Mohs scale) from that which measures compressive strength, such as, among others, Young's Modulus. Compressive strength measures the amount of pressure that any solid substance, pure or composite, can withstand when a piece (usually a sphere of high-carbon steel or even another diamond) is applied directly to the sample, pushing it with great force, up to several gigapascals of pressure. In this sense, diamond is indeed "invincible," or at least among the solids with the greatest resistance to breakage by compression. However, its fragile nature becomes apparent again when an impact of sufficient mass is applied to it (a household hammer would do the job). The fact that you don't find videos or supposed evidence of its volatile nature is due, first of all, to the fact that no one would "sacrifice" an expensive diamond simply to demonstrate that it is, in fact, fragile, that is, not tenacious. That said, ask anyone who has ever worked with diamonds (typically gemologists who cut them) and you'll see that, while this gem is very difficult to cut, it is by no means an "indestructible" material. It's quite possible that the fact that diamonds have this reputation is due more to popular culture and marketing that has championed slogans like "Diamonds are forever," which isn't true even from the perspective of carbon phase equilibrium. But I understand that the gem's power as a symbol of high status and wealth is not going to be lost just like that. In short: Diamond has the highest Mohs hardness (resistance to wear due to friction/abrasion) and one of the highest resistance indices in tests that measure the ability to withstand concentrated weight (compressive strength, e.g., Young's modulus), but its resistance to impact (hammer blows, drops, collisions) is higher than average for other crystals, but much lower than that of metals or metal alloys. I sincerely hope I've explained myself well, because although most consider it silly, it is one of the details that motivated me to write this book.

Another outstanding characteristic of Diamond, seen as a gem, is its great capacity for light dispersion. This means that Diamond reacts with sunlight in such a way that, if cut properly (an example is the classic Diamond cut), it results in the reflection of the incoming light, achieving a dazzling "mirror" effect. This ability to shine is called by the same word in English and Spanish: "fire" for them and "fuego" for us. Of all the gems that can be found naturally, the diamond excels in this regard, which is why, for centuries and even to this day, it continues to be preferred over other gems. Not only this, but the diamond itself, at least in theory, is transparent (a sign that it is chemically pure), in contrast to other gems whose color defines themselves, namely, red for the ruby, blue for the sapphire, and green for the emerald. None of the three shines as intensely as the transparent diamond (although there are diamonds of many colors); the crystalline one is the most valued, except for black or exotic colored varieties that command a higher price due to their rarity rather than their properties. As I said before, the "ideal diamond," so to speak, is transparent, crystalline.

You've seen me say before that the "fire" (light-dispersion capacity) of diamonds is the highest among natural gems. Well, synthetic cubic zirconia (the diamond imitator par excellence) possesses even more "fire," although it lacks the hardness and compressive strength of diamonds. Today, it's so popular that, although it was initially considered a "cheap imitation" on the market, its popularity, so to speak, is increasing every day. Proof of this is that many of the jewelry worn by wealthy people features zirconias instead of diamonds, especially when it comes to luxury items that, instead of a few pieces, number in the hundreds or even thousands. Examples such as these are cars, handbags, shoes, and jackets "paved" with hundreds of zirconias, giving them that "diamond-like" appearance. Chemically, diamond is very resistant to corrosion (more so than graphite) and is unaffected by the vast majority of liquid or gaseous substances at room temperature and pressure, which is not the case with other gems, which do deteriorate under certain conditions. However, diamond, being elemental carbon, greatly favors bonding with oxygen, so a piece subjected to temperatures above 500°C will begin to react, releasing heat and forming CO2 (carbon dioxide). You would be surprised to know that this is precisely what happened when a diamond was burned, as Lavoisier did in 1772 when he exposed one to sunlight concentrated in lenses, like a magnifying glass, only much more powerful.

The price of diamonds is known by all as one of the highest among all solid substances due to its excellent properties, which make it the best among gems. This has made it the object of endless searches for centuries and a source of dispute (which is why it is considered a conflict material). The largest reserves are in South Africa, and to a lesser extent, the Urals and the eastern border of the United States with Canada.

For years, attempts have been made to imitate the gem's properties (especially its intense brilliance) with varying success. The aforementioned cubic zirconia, with a chemical composition of ZrO2, is by far the most successful, as it is relatively cheap to produce and requires fewer expensive requirements than other imitations. A second gem considered similar to diamond is moissanite, which, although we can find it naturally, is usually synthesized in laboratories. It is not very well known and is named after the French chemist of Jewish origin, Henri Moissan, who isolated fluorine for the first time in 1886. Moissanite is simply silicon carbide, with an internal crystalline structure identical to that of diamond. It can be mass-produced, as is the case with the ceramic of the same name currently used to manufacture high-end automobile brakes, among other things, but the purest form, which is transparent, demands more requirements to achieve sufficient clarity to reach "gem level." It is harder than corundum (sapphires, rubies, etc.) but less so than real diamonds.

Finally, there are artificial diamonds, which share the same characteristics as pure diamonds, except for their size (so far, they can only be produced in sizes similar to grains of sand) and their complete lack of transparency, which rules them out for use as gems.

The diamond market has many clients, but it is a closed consortium between mainly Dutch and English companies that generate billions each year.

The importance of diamonds as gems is so great that they are rarely considered an important part of the industry. Below, we will look at some of their excellent properties and respective applications.

It is the solid substance, pure or compound, with the highest thermal conductivity of all known materials (much more than any metal, even silver), so it finds applications in equipment requiring high thermal conductivity and good resistance to wear and chemical attack, such as, for example, in the electronics sector.

Its great hardness makes it the ideal abrasive, and therefore it is used as such in cutting and filing operations in industry. The diamonds used in these areas are natural but very small, that is, waste from the mines themselves, or directly artificial. They are applied to other compounds, such as steel sheets, or are pulverized and applied like sandpaper. They are also used directly, projected as granules through a water jet (usually water) used for cutting. In this case, the water propels the diamonds while simultaneously serving as a coolant. It should not be forgotten that friction through abrasion generates a lot of heat, which can be harmful under certain conditions.

Since diamond easily scratches any other solid, it is not only used as an abrasive for cutting but also, among other things, for engraving metal surfaces. This is the case with many steels or tungsten carbide in its jewelry form, and fashion rings that are "signed" with small diamond points. Likewise, low-quality diamond (as a gem) is used to cut other less hard gems such as sapphire, ruby, emerald, and so on, since its hardness does not vary substantially between natural and artificial varieties.

Another characteristic of diamond, as opposed to graphite, is that while graphite conducts electricity well but not heat, diamond conducts heat better than any other, but is an electrical insulator, that is, a poor conductor of electricity. Because of this, it is used as an insulator in some applications.

Diamond, a crystalline allotrope of carbon (C) with a Mohs hardness of 10 on the Mohs scale, is the hardest known natural material, making it an invaluable resource in industrial applications requiring wear resistance, precision, and durability. Its cubic structure (sp³ hybridization), high thermal conductivity (2,000–2,500 W/m K), and low electrical conductivity (10⁻¹⁵ S/m) complement its versatility, enabling uses beyond jewelry, which consumes ~10–20% of natural diamonds, while the industrial sector uses ~80–90% of global production (130 million carats or 26 tonnes annually). With a density of 3.52 g/cm³ and a carbon abundance of ~200 ppm in the Earth's crust, industrial diamonds, both natural and synthetic, are essential in sectors such as manufacturing, mining, electronics, and scientific research, thanks to their ability to withstand extreme conditions.

Diamonds' primary use in industry is in cutting, drilling, and abrasive tools, where their exceptional hardness allows them to work materials such as metals, ceramics, rocks, and composites. Industrial diamonds, often of lower quality than jewelry diamonds (with flaws or reduced clarity), are embedded in saws, drill bits, grinding wheels, and grinding tools used in mining, construction, and precision parts manufacturing. For example, in oil and gas extraction, diamond-tipped drill bits drill through hard rock formations, such as granite or basalt, with an efficiency that surpasses high-strength steels. Synthetic diamonds, produced by chemical vapor deposition (CVD) or high-pressure, high-temperature (HPHT), dominate this market (50% of industrial diamonds) as they are cheaper ($1,000/carat versus $5,000–$10,000 for natural gems) and can be designed into specific shapes for applications such as glass cutting or surface polishing.

In electronics, diamonds are valued for their thermal conductivity and insulating properties. They are used as heat sinks in high-power devices such as lasers and semiconductors, where they dissipate the generated heat without conducting electricity, protecting sensitive components. Boron-doped (B) diamonds are developed into semiconductors, with emerging applications in high-frequency transistors and radiation detectors. In optics, diamond windows, especially synthetic ones, are essential in high-energy laser systems and infrared spectroscopy, as they are transparent over a wide range of wavelengths (UV to IR) and resist radiation damage. In scientific research, diamonds are used in diamond anvil cells (DACs) for high-pressure experiments, recreating conditions in the Earth's mantle (up to 100 GPa) to study materials or simulate planetary environments.

The production of synthetic diamonds has transformed industrial uses, reducing dependence on natural diamonds, which come primarily from Russia, Botswana, and South Africa. CVD and HPHT methods make it possible to manufacture diamonds with controlled properties, such as size, purity, and shape, at a significantly lower cost, expanding their accessibility for industrial applications. For example, polycrystalline diamond (PCD) black is used in cutting tools for machining aluminum (Al) alloys in the automotive and aerospace industries. Although gem-quality natural diamonds remain coveted in jewelry, industrial and synthetic diamonds dominate the tool and technology market, representing a much larger volume. Diamond's durability, chemical resistance (immune to acids such as HNO₃ and HCl), and thermal properties ensure its critical role in modern industry, from mining to cutting-edge electronics, cementing it as an indispensable material beyond its aesthetic brilliance.

Diamonds, crystalline allotropes of carbon (C) and the hardest known natural materials (10 on the Mohs scale), have been synonymous with rarity, luxury, and value for centuries. Their brilliance, durability, and association with exclusivity have made them a mainstay of jewelry and a cultural symbol of wealth. However, the perception of their scarcity has been a subject of debate, influenced by both geological factors and marketing strategies. Are diamonds really as rare as their price and prestige suggest, or is this rarity partly an artificial construct? This article explores the geological abundance, production, market, and historical factors that shape the perception of diamonds.

In geological terms, diamonds are rare compared to other common minerals, but not as scarce as is often believed. Carbon, its constituent element, has an abundance of 200 ppm in the Earth's crust, but diamond formation requires extreme conditions: high pressures (4.5–6 GPa) and temperatures (900–1,300 °C), typical of the Earth's mantle at depths of 150–200 km. These conditions are found in cratons, geologically stable regions, where diamonds form and are transported to the surface by volcanic eruptions in structures called kimberlites or lamproites. Their density (3.52 g/cm³) and cubic structure (sp³ hybridization) make them exceptionally resistant, but their natural occurrence is limited to specific deposits in countries such as Russia, Botswana, Australia, Canada, and South Africa, which represent ~80% of global production (130 million carats or 26 tons per year). Although diamonds are less abundant than minerals such as quartz or feldspar, their presence in the Earth's crust is more common than the general public realizes. For example, kimberlite deposits contain diamond concentrations of 1–5 parts per million (ppm), and only a fraction of these are gem-quality (suitable for jewelry), while the remainder are industrial diamonds, used in cutting tools due to their hardness. Geological rarity, therefore, is relative: gem-quality diamonds, especially those of large size or exceptional purity (such as those graded D for color and IF for clarity), are significantly rarer, representing less than 1% of total production. However, the total abundance of diamonds, including industrial diamonds, is greater than the luxury market suggests.

The perception of diamond scarcity has been largely shaped by marketing strategies, especially by De Beers, a company that dominated the global market for much of the 20th century. Since its founding in 1888, De Beers controlled up to 90% of global diamond production, regulating supply by building up reserves and limiting distribution to maintain high prices. In 1947, the “A Diamond is Forever” campaign cemented the image of the diamond as a rare and eternal commodity, linking it to betrothal and increasing demand. This marketing strategy, combined with monopolistic control of mines and distribution channels, created an artificial scarcity that drove prices higher than geological abundance would justify. Today, diamond production is more diverse, with countries such as Russia (ALROSA) and Botswana leading the supply, and De Beers’ market share has declined to ~30%. Global natural diamond production remains stable at ~120–140 million carats per year, with a market value of ~14 billion USD (2025). Furthermore, synthetic diamonds, produced through chemical vapor deposition (CVD) or high-pressure, high-temperature (HPHT), have flooded the market since the 2000s. These diamonds, chemically identical to natural diamonds, represent ~10% of the jewelry market and up to 50% of the industrial market, with significantly lower prices (a 1-carat synthetic diamond costs ~1,000 USD versus ~5,000–10,000 USD for a natural one). This innovation has reduced the perception of scarcity, especially for low-quality diamonds, although high-quality natural diamonds remain coveted.

The idea of ​​diamond scarcity is also rooted in their cultural history. Known since ~3000 BC, In India, diamonds were valued for their rarity and symbolism, used in jewelry and as talismans for their hardness and brilliance. Until the 18th century, India was the main source, with mines like Golconda producing legendary gems such as the Koh-i-Noor. The discovery of deposits in Brazil (18th century) and South Africa (19th century) increased supply, but De Beers' control prevented a price crash. The narrative of rarity was reinforced by stories of unique gems and the exclusivity of the "four Cs" (carat, clarity, color, cut), which emphasize the uniqueness of each diamond.

However, perceived scarcity does not always reflect reality. Gem-quality diamonds are rare in absolute terms, but the mass production of industrial and synthetic diamonds has saturated certain market segments. Furthermore, ethical conflicts associated with “blood diamonds” in regions like Sierra Leone have led to regulations such as the Kimberley Process (2003) that restrict the trade in conflict diamonds, marginally affecting supply. The growing acceptance of synthetic diamonds, promoted as ethical and sustainable, also challenges the rarity narrative, as their production is scalable and does not rely on limited geological deposits.

Diamonds are geologically rare due to the extreme conditions necessary for their formation, but their scarcity has been amplified by commercial and cultural strategies. While gem-quality diamonds, especially those of large size or exceptional clarity, are genuinely scarce (less than 1% of production), the abundance of industrial diamonds and the production of synthetics have reduced their overall exclusivity. In 2025, the market reflects this duality: high-quality natural diamonds maintain high prices (~$10,000/carat for premium gems), while synthetic and industrial diamonds are significantly more accessible. Diamond scarcity, therefore, is both a geological reality and a market construct, shaped by history, economics, and cultural perception. For consumers, the decision between a natural or synthetic diamond depends not only on their budget but also on the values ​​they prioritize: exclusivity, ethics, or sustainability.