Where Natural Diamonds Are Found
Natural diamonds form deep within the Earth, typically at depths ranging from 90 to 120 miles, under immense pressure and high temperatures. These conditions exist within the Earth’s mantle. Geological processes eventually bring them closer to the surface.
The primary way these diamonds are brought to the Earth’s surface is through volcanic eruptions that form kimberlite pipes. Kimberlite is an igneous rock that originates deep in the mantle and erupts explosively, carrying diamonds upward. These pipes represent the main source of commercially mined diamonds.
Erosion can wear down these kimberlite pipes, releasing the diamonds from their primary rock matrix. Rivers and streams then carry these diamonds away from their original source, depositing them in new locations. These secondary deposits, known as alluvial deposits, are found in riverbeds, lakebeds, and coastlines, where they accumulate due to their density and resistance to weathering.
The Appearance of Raw Diamonds
Raw, uncut diamonds look very different from the sparkling gemstones seen in jewelry. In their natural state, they typically have a greasy or waxy luster. Their surfaces can appear rough or frosted, often covered with a dull, opaque film or growth marks.
The most common crystal shape for natural diamonds is an octahedron, resembling two pyramids joined at their bases. Other forms include dodecahedrons, which have 12 faces, and cubes, although these are less common.
Natural diamonds come in a wide range of colors, many of which are not the clear, colorless variety associated with finished gems. Common natural colors include yellowish, brownish, or gray hues, due to impurities like nitrogen. Blue diamonds contain boron, while green diamonds are exposed to natural radiation.
Raw diamonds may also contain visible inclusions, which are tiny minerals or other diamonds trapped within the crystal during its formation. These internal features, along with external growth marks or pits, contribute to the unique character of each raw stone. Unlike cut diamonds, raw diamonds do not refract light in the same way and appear much more unassuming.
Identifying Natural Diamonds in the Wild
Identifying natural diamonds in the wild without specialized equipment can be challenging. One defining characteristic is their extreme hardness, ranking 10 on the Mohs scale, making them the hardest naturally occurring mineral. Diamonds can scratch almost any other material, though attempting a scratch test is not advisable as it can damage other materials and might not be conclusive for an untrained individual.
Diamonds also possess a high specific gravity, meaning they are denser than many other minerals of similar size. For instance, a diamond will feel heavier than a piece of quartz of the same volume. This density causes them to sink quickly in water, distinguishing them from lighter minerals that might float or suspend.
Another property is their thermal conductivity; diamonds are exceptional heat conductors. A simple test, often used by jewelers, involves placing a diamond on a cold surface or breathing on it; a real diamond will quickly dissipate heat and clear condensation rapidly, unlike most simulants like cubic zirconia or glass. While these characteristics offer clues, definitive identification usually requires professional tools and expertise to confirm a diamond’s authenticity.