Each of these crystals, each diamond, one carat diamond, represents literally billions and billions of carbon atoms that all had to lock into place to form this very orderly crystalline structure. You mentioned that scientists don't know where the carbon comes from.
What are some possible sources? In some cases, the carbon seems to have originated within the mantle of the Earth, so carbon that was already in the Earth. In other cases, there's evidence very curiously to suggest that the carbon may have originated near the surface of the Earth. The thinking there is that this carbon could have literally been carbon that was part of carbonate sediments or animals, plants, shells, whatever, that was carried down into the upper mantle of the Earth by the plate tectonics mechanism called subduction.
We really don't know how long it takes. There have been attempts to try to date inclusions in different parts of diamonds, and those have largely been unsuccessful.
It may be that diamonds form over periods as short a time as days, weeks, months to millions of years. Typically, as with many crystals that grow on the Earth, it's not a continuous process. The diamonds may start to grow and then there may be an interruption for some reason — a change in conditions, temperature, pressure, source of carbon, whatever—and they could sit for millions, hundreds of million of years, and then start growing again.
That's part of the problem of trying to put some sort of a growth period on them; things don't always occur continuously in the Earth. We can grow diamonds in the lab and we can simulate conditions there. But there are things we have to do to grow diamonds in the laboratory that aren't obvious as to how it happens in the Earth. In the laboratory, they're typically grown, but there's some catalyst.
Some metals are often added to cause the diamonds to grow, but these same catalysts are not observed in the diamonds from the upper mantle of the Earth. All diamonds, as far as we know, are quite old in the Earth. Most diamond formation probably took place in the Earth in the first couple billion years of the Earth's history. There are diamond deposits that have been discovered that are younger—the rock itself, the Kimberlite, is maybe just tens of hundreds of millions of years old.
The way they date diamonds is typically looking at inclusions of other minerals in the diamond that can be radioactively dated. The diamonds themselves can't be dated. Another problem with the idea is that coal seams are sedimentary rocks that usually occur as horizontal or nearly horizontal rock units. However, the source rocks of diamonds are vertical pipes filled with igneous rocks. Four processes are thought to be responsible for virtually all of the natural diamonds that have been found at or near Earth's surface.
The remaining three are insignificant sources of commercial diamonds. Diamonds from Deep-Source Eruptions: Most commercial diamond deposits are thought to have formed when a deep-source volcanic eruption delivered diamonds to the surface.
In these eruptions, magma travels rapidly from deep within the mantle, often passing through a diamond stability zone on its route to the surface. Pieces of rock from the diamond stability zone may be torn free and carried rapidly upwards to the surface.
These pieces of rock are known as "xenoliths" and may contain diamonds. Geologists believe that the diamonds in all of Earth's commercial diamond deposits were formed in the mantle and delivered to the surface by deep-source volcanic eruptions. These eruptions produce the kimberlite and lamproite pipes that are sought after by diamond prospectors.
Most of these pipes do not contain diamond, or contain such a small amount of diamond that they are not of commercial interest. However, open-pit and underground mines are developed in these pipes when they contain adequate diamonds for profitable mining.
Diamonds have also been weathered and eroded from some of these pipes. Those diamonds are now contained in the sedimentary placer deposits of streams and coastlines. The formation of natural diamonds requires very high temperatures and pressures.
These conditions occur in limited zones of Earth's mantle about 90 miles kilometers or more below the surface, where temperatures are at least degrees Fahrenheit degrees Celsius [1]. The critical temperature-pressure environment for diamond formation and stability is not present globally.
Instead it is thought to be present primarily in the mantle beneath the stable interiors of continental plates [2].
Diamonds formed and stored in these "diamond stability zones" are delivered to Earth's surface during deep-source volcanic eruptions. These eruptions tear out pieces of the mantle and carry them rapidly to the surface [3].
See Location 1 in the diagram at the top of the page. This type of volcanic eruption is extremely rare and has never been observed by modern humans. Is coal involved? Coal is a sedimentary rock, formed from plant debris deposited at Earth's surface. It is rarely buried to depths greater than two miles 3. It is very unlikely that coal has been moved from the crust down to a depth well below the base of a continental plate. The carbon source for these mantle diamonds is most likely carbon trapped in Earth's interior at the time of the planet's formation or delivered to great depths by subduction.
Diamonds From Ocean Sediments? Subduction zones occur at convergent plate boundaries where one plate is forced down into the mantle. As this plate descends, it is exposed to increasing temperature and pressure. Diamonds have been found in rocks that are thought to have been subducted and then returned to the surface.
These types of rocks are very rare, and no known commercial diamond deposits have been developed within them. The diamonds found in these types of deposits have been very small and not suitable for commercial use. Tiny diamonds have been found in rocks that are thought to have been subducted deep into the mantle by plate tectonic processes - then returned to the surface [4]. See Location 2 in the diagram at the top of the page. Diamond formation in a subducting plate might occur as little as 50 miles 80 kilometers below the surface and at temperatures as low as degrees Fahrenheit degrees Centigrade [1].
In another study, diamonds from Brazil were found to contain tiny mineral inclusions consistent with the mineralogy of oceanic crust [8]. Others have inclusions that suggest that subducted seawater was involved in their formation [9]. A more recent study investigated the origin on blue, boron-containing diamonds that formed at depths as great as miles kilometers.
These super-deep diamonds also contained inclusions indicating that they were derived from subducted oceanic crust. Coal is not a probable carbon source for this diamond-forming process. The most likely carbon sources from the subduction of an oceanic plate are carbonate rocks such as limestone , marble , and dolomite , and possibly particles of plant debris in offshore sediments. Lab diamonds are grown from a carbon seed, like flowers in a greenhouse.
The short answer is yes, humans can make man made diamonds or lab grown diamond stimulants. In this process, a small slice of diamond seed which is often a HPHT produced diamond is placed in a chamber and heated to extreme temperatures, much like a rough diamond would undergo in the ground.
The chamber is then filled with gases that help form the diamond, like methane. The gases are ionized into plasma using lasers. The ionization breaks the molecular bonds and the carbon adheres to the diamond seed, slowly crystalizing. The final result is a crystalized carbon structure, exactly the same as a mined diamond.
The High Temperature High Pressure method is still widely used and results in the same product. One of three manufacturing processes are used in this method: a belt press, cubic press and split-sphere press. All three of these processes create an environment of high pressure and temperature.
In this method, a diamond seed is placed into carbon. Using one of the three methods, it is then exposed to temperatures around degrees Fahrenheit and pressurized to approximately 1. The carbon melts and starts to form a diamond starter seed. Once the cooling process is finished, the result is a crystalized carbon structure.
Diamond alternatives are simulant stones that resemble diamonds, but are chemically distinct. There are many options on the market today, such as cubic zirconia, morganite and amethyst. Each stone features completely different characteristics as they are made out of different materials. CZ is one of the most common diamond alternatives on the market, commonly seen in inexpensive jewelry. Although a well-cut CZ may look similar to a diamond at first, it is much more porous than a diamond, which causes it to absorb contaminants and dull over time.
Nexus Diamonds are made of a proprietary formula and patented coating material which causes them to reflect light at a much closer rate to diamonds than all other simulants. The final product is a stone that is harder, heavier and less porous than other alternative stones, making it much more similar to a colorless, flawless diamond.
The diamond simulant creation process begins similar to the lab diamond process. A proprietary blend of elements is heated to extreme temperatures. The elements then reach a molten state. The next step is to carefully cool the molten matrix in controlled stages that allow crystals to form. This is one of the most critical phases in creating diamond simulants. If cooled too slowly, crystals will not form; if cooled too quickly, crystals will shatter.
Following the cooling stage, a solid object containing both crystallized and non-crystallized material will be left. The crystals are a hard, heavy, dense material that closely resembles the look of an uncut diamond crystal. The crystals are inspected for quality in a similar way to how rough diamonds are inspected and graded using the 4Cs.
After the stones are rough cut, they contain no inclusions or other flaws. They are sorted and moved to the final cutting stage. Because each crystal is flawless, our master cutters can be much more precise, because they are not trying to cut around and hide flaws.
Our diamond simulants are then coated in a patented coating material, which seals them completely and makes them even harder and non-porous. The coating finishes the diamond simulant creation process. Each of these stone options are created in different ways, which results in different characteristics.
The differences between the two stone options come down to price point, environmental damage and ethical concerns. Because lab diamonds are fairly new to the market, they are currently less expensive than mined diamonds. With lab diamonds, environmental concerns are almost eliminated.
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