However, Gemstones created in lab are not imitations.For example, diamonds, ruby, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics as with the naturally occurring variety. Synthetic corundums, including ruby and sapphire, are very common and they cost only comparatively lesser than the natural stones. Smaller synthetic diamonds are manufactured in large quantities as industrial abrasives.In addition larger synthetic diamonds of gemstone quality, especially of the colored variety, are also manufactured.
Some gemstones are manufactured in order to imitate other gemstones. As an example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. Moissanite is another similar example. The imitations copy the look and color of the real ones but possess neither their chemical nor physical characteristics.
Whether a gemstone is a natural stone or a lab-created stone, the characteristics of each are similar. Lab-created stones usually tend to have a more vivid color to them, as impurities are not present in a lab, so therefore do not affect the clarity or color of the stone.
Heat can improve gemstones color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is commonly practiced. Most citrine is made by treating amethyst with heat and partial heating with strong gradient results in ametrine - a stone partly amethyst and partly citrine. Much aquamarine is heat treated to remove yellow tones and to change the green color into the more desirable blue or enhance its existing blue color to a purer blue. Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more suitable blue/purple color. A considerable portion of all sapphire and ruby is treated with various heat treatments to improve both color and clarity.
When jewelry containing diamonds is heated the diamond should be protected with boracic acid; else the diamond could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies is heated up, it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.
The market for industrial-grade diamonds operates very much differently from its gem-grade counterpart. Industrial diamonds are mostly valued for their hardness and heat conductivity, making many of the gemological characteristics of diamonds, such as clarity and color, irrelevant for most applications. This helps explain why 80% of mined diamonds are unsuitable for use as gemstones, are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 570 million carats (114 tons) of synthetic diamond is produced annually for the industrial purpose. Approximately 90% of diamond grinding grit is basically of synthetic origin.
The boundary between gem-quality diamonds and industrial diamonds is partly defined and partly depends on market conditions. Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are called as bort.
Industrial use of diamonds has been historically associated with their hardness; this property makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including the other diamonds. Common industrial adaptations of this typical ability include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive. Less expensive industrial-grade diamonds, known as bort, with more flaws and poorer color than other gems, are used for such purposes. Diamond is not suitable for machining ferrous alloys at high speeds, as carbon is soluble in iron at the higher temperatures created by high-speed machining, leading to largely increased wear on diamond tools when compared to other alternatives.
Specialized applications involve use in laboratories as containment for high pressure experiments, high-performance bearings, and limited use in specialized windows. With the continuing advances being made in the production of synthetic diamonds, future applications have become feasible. Garnering much excitement is the main use of diamond as a semiconductor suitable to build microchips, or the use of diamond as a heat sink in electronics.
Diamond clarity is a quality of diamonds related to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Clarity is the important one of the four Cs of diamond grading, the others being carat, color, and cut. Inclusions may either be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. Factors such as the number, size, color, relative location, orientation, and visibility of inclusions can affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone less than 10x magnification.
Most inclusions that are present in gem-quality diamonds don't affect the diamonds' performance or structural integrity. However, large clouds can in turn affect a diamond's ability to transmit and scatter light. Large cracks that are close to or breaking the surface may reduce a diamond's resistance to fracture.
Usually diamonds with higher clarity grades are more valued, with the exceedingly rare "flawless" graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can also be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamond technology improves and distinguishing between natural and synthetic diamonds becomes very difficult, inclusions or blemishes can be used as proof of natural origin.
Diamonds form between 120-200 kms or 75-120 miles deep in the earth's surface. According to geologists the first delivery of diamonds was somewhere around 2.5 billion years ago and the latest was 45 million years ago. According to science, the carbon that makes diamonds comes from the melting of pre-existing rocks in the Earth's upper surface mantle. There is an abundant quantity of carbon atoms in the mantle.
Temperature changes in the upper mantle forces the carbon atoms to go deeper and it melts and finally becomes new rock, when the temperature reduces. If other conditions like pressure and chemistry works right then the carbon atoms in the melting crustal rock bond to build diamond crystals. Yet there is no guarantee that these carbon atoms will surely turn into diamonds. Either if the temperature rises or the pressure drops then the diamond crystals may melt partially or totally dissolve. Even if they do form, it would take thousands of years for those diamonds to come anywhere near the surface.
Color is the most impressive and attractive feature of gemstones. The color of any material is the result of the nature of light itself. Daylight, often termed as white light, is actually a mixture of different colors of light. When light passes through a material, some of them may be absorbed, while the rest passes through. The part which is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light - blue, yellow, green, etc. – other than red.
The same material can exhibit various different colors. For example ruby and sapphire have the same chemical composition, but they exhibit different colors. Though the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".
This difference in color depends on the atomic structure of the stone. Although the different stones have the same chemical composition formally, they are not exactly the same. Every now and then an atom is completely replaced by a totally different atom. These so called impurities are enough to absorb certain colors and leave the other colors unaffected.
For an example: beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, it becomes pink morganite. Added with iron, it becomes aquamarine. Some gemstone treatments make use of these facts thus changing the color of the gem.
Diamond enhancements are certain peculiar treatments performed on natural or synthetic diamonds, usually those already cut and polished into a gem, which are designed to better the gemological characteristics of the stone in one or more ways.
These techniques generally include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.
In addition, coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is carbon-an amorphous carbonaceous material, which looks like a diamond that has some physical properties similar to those of the diamond. Advertising suggests that such kind of coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. Techniques such as Raman spectroscopy should easily identify such type of treatment.
Early diamond identification tests included a scratch test which relied completely on the superior hardness of diamond. Yet this test is destructive, as a diamond can scratch diamond, and is rarely used nowadays. Instead, Diamond identification can also rely on its superior thermal conductivity. Electronic thermal probes are commonly used in the gemological centers to separate diamonds from their imitations. They consist of a pair of battery-powered thermistors mounted in a fine copper tip in which one functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes around 2–3 seconds.
Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond irradiated or non-irradiated, etc., requires more advanced, optical techniques. These techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test. Optical techniques can distinguish between natural diamonds and synthetic diamonds. "Perfect" crystals have never been found, so both natural and synthetic diamonds always possess characteristic imperfections, arising from the circumstances of their crystal growth, that allow them to be distinguished from each other.
Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to find out a diamond's origin. They also include specially made machines to aid them in the identification process. Two screening machines are the Diamond Sure and the Diamond View, both are produced by the DTC and marketed by the GIA.
Several methods for identifying the synthetic diamonds can be performed, depending on the method of production and the color of the diamond. CVD diamonds can generally be determined by an orange fluorescence. D-J colored diamonds can usually be screened through the Swiss Gemological Institute’s Diamond Spotter. Similarly, natural diamonds usually have minor imperfections and flaws that are not seen in synthetic diamonds.
Exploration diamond drilling differs from other geological drilling where in that a solid core is extracted from depth, for examination on the surface. The key technology of the diamond drilling is the actual diamond bit itself. It is usually composed of industrial diamonds set into a soft metallic matrix. The diamonds are scattered all over the matrix, and the action relies on the matrix to slowly wear during the drilling, so as to expose more diamonds.
The bit is mounted onto a drill stem, which is in turn connected to a rotary drill. Water is injected into the drill pipe in order to wash out the rock cuttings produced by the bit. An actual diamond bit is a complex affair with many channels for washing.
The drill uses a diamond encrusted drill bit to drill through the rock. The drill produces a "core" that is photographed and split longitudinally. Half of the split core is kept under analysis while the other half is permanently stored for future use if necessary. A larger diameter core is the most preferred yet it is the most expensive. The commonly preferred diameter sizes of core are NQ and CHD 76.
A diamond simulant is generally a non-diamond material which is used to simulate the appearance of a diamond. Diamond-simulant gems are usually called as diamante. The most popular diamond simulant to most consumers is cubic zirconia.
The popular gemstone moissanite is quite often treated as a diamond simulant, although it is a gemstone in its own right. While moissanite seems similar to diamond, its main disadvantage as a diamond simulant is that cubic zirconia is much cheaper and arguably equally convincing. Generally both are produced synthetically.
The mined rough diamonds are usually converted into gems & jewelleries through a multi-step process called "cutting".
Diamonds are extremely hard, yet so brittle and can be easily split up by a single blow. The diamond cutting is traditionally considered as a delicate procedure requiring skills, scientific knowledge, tools and experience. Its final goal is to produce a faceted precious jewel where the specific angles between the facets would optimize the diamond luster that is dispersion of white light, whereas the number and area of facets would determine the weight of the final product.
The most time-consuming part of the cutting is the preliminary analysis of the raw stone. It needs to address several issues, bears much responsibility, and therefore can last years in case of unique diamonds. The following issues are considered:
The hardness of diamond and its ability to cleave strongly depend on the crystal orientation. Therefore, the crystallographic structure of the diamond to be cut is analyzed with the help of X-ray diffraction in order to choose the optimal cutting directions.
Most diamonds contain various visible non-diamond inclusions and crystal flaws. The cutter has to decide which flaws are to be removed by the cutting and which could be left undisturbed.
The diamond can be split by a single, well calculated blow of a hammer to a pointed tool, which is quick, yet risky. Alternatively, it can be cut using a diamond saw, which is a more reliable but tedious procedure.
Naturally, there are two types of diamond deposits: primary and secondary deposits. Primary deposits are those in which the diamonds stay inside the original host rock (usually kimberlite) that expressed them to the surface. Secondary deposits are formed when the diamonds are battered from the host rock and concerted by the deed of water into alluvial deposits (in rivers) or marine deposits (in beaches).
In diamond searching, it is commonly accepted that economic primary diamond deposits are connected with ancient shields or "cratons". These cratons are large in size, coherent expanses of rock that have been physically stable for at least one billion years. Cratonic "keels" underneath these formations can expand to depths within the earth's layer wherever pressure and temperature conditions are favourable to diamond formation and preservation. The formation of these diamondiferous keels is composite which is one reason why kimberlites devoid of diamonds can occur in close proximity to luxuriantly diamondiferous ones.
