Why does a diamond sparkle so brilliantly? How is it formed? What makes it so rare?
This past Friday, I learned the answers to these questions and much more during my class on diamonds at L’École Van Cleef & Arpels at the Cooper Hewitt museum in New York. Segmented into two parts, the four hour course revealed the scientific secrets of diamonds and how man has learned to tame this invincible stone. Our fearless instructor for the afternoon was Dominique Dufermont, a gemstone expert and buyer with dual training in geology and gemology.
After we settled into our seats, Mr. Dufermont wasted no time in revealing the four secrets of a diamond, beginning with The Essence of Life. This segment explained the diamond’s highly organized atomic structure, the differences between it and its fake twin graphite, and a chemistry refresher on the element carbon. Did you know that a diamond is the only mono-element mineral? I didn’t! As we eased into the next segment, I felt like the cobwebs clouding my chemistry knowledge from high school and college had just received a light dusting.
Going back to the cosmic origins of carbon, Mr. Dufermont explained the precise ingredients required to create a natural diamond in The Improbable Epic. Those ‘ingredients’, or very specific conditions, are carbon, several thousand atmospheres of pressure (between 45 and 60 kilobars), a temperature of more than 1,832 °F but below 2,370 °F, and less than 5% acidity in the molten rock in which the diamond will form. Such extreme pressure, plus the other required conditions, occurs at a depth between 140 and 190 kilometers (87 and 118 miles). There, diamonds bake in earth’s volcanic oven until it surfaces by way of magma in a volcanic pipe. Historically, most diamonds were found in alluvial deposits but mining in kimberlite pipes has proven highly – though relatively – productive as well. I say relatively because it requires an eye-opening ten tons of rock for every carat of diamond recovered. What’s more fascinating is that 95 percent of all diamonds mined are used for industrial purposes, which means only 5 percent is of gem quality. Of that 5 percent, only 3 percent meet the high quality standards of the most prestigious jewelry houses. Calculating everything together, a mere 0.15 percent of all diamonds mined are of the utmost quality for the most coveted jewels in the world. Ultimately, the complicated processes necessary to recover the earth’s diamonds are what makes them rare and valuable. Rarity is relative.
With a newer, more profound appreciation for the diamond in my engagement ring, I was ready to learn about the diamond’s Unique Hardness. In this portion, those cobwebs received an even more intense dusting as Mr. Dufermont explained the scientific properties that render the diamond the hardest natural material on earth: the powerful strength of covalent bonds between carbon atoms, its three dimensional cubic structure, the extreme atomic density of the diamond’s face-centered cubic crystallization, and the diamond lattice of interlocking network of the tetrahedrally bonded carbon atoms. For further explanation of these technical fragments, be sure to sign up for the course because Mr. Dufermont is way more capable and eloquent in explaining this than I could ever hope to be!
Deep in science mode, we explored the diamond’s Incomparable Light with a hands-on demonstration. A box with three round stones was given to each pair of students, and we were instructed to study the differences between them and then determine which was the diamond. The major giveaway was, of course, the diamond’s brilliance. The unrivaled sparkle of a diamond is a result of its mirror effect, or capacity for reflecting light, and its dispersion effect, or capacity to separate light waves. Of the three stones in the box (I won’t reveal what they were for the sake of future participants), the diamond has the highest refractive index.
At this point, we were in need of a break and luckily the class anticipated this. Before beginning the second part of the class, we migrated back to the beautiful L’École lounge/library for refreshments. Stay tuned for the second part of the class tomorrow!