Unlike in some sectors of the diamond industry, rough sorting and price evaluation are still largely done by skilled people examining the diamonds. Walk into any rough diamond sorting room, and you will find a few standard tools that are used almost universally to assist in classifying rough stones. In the past few years, however, new technology has been developed that is helping automate rough sorting, especially for smaller diamonds that are laborious to sort manually.
Other minerals that can infiltrate a parcel of diamonds can sometimes fool even the most skilled rough sorter. This is especially true of smaller diamonds, which tend to be present in huge quantities. Diamond testers are a tool to help sorters establish if a questionable stone is indeed a diamond, or a similar-looking stone such as silicate. Diamond testers work by sending heat into the stone, and by measuring how quickly the stone conducts the heat. Each type of mineral has its own unique conductivity signature, and this helps determine if the stone is indeed a diamond. The one drawback to diamond testers is that for the moment, many of them cannot distinguish between diamonds and moissanite, a common substitute for diamonds that requires a separate tool to evaluate.
Color machines are a useful supplement to the human eye. They establish the color of a rough or polished stone, and also identify other characteristics, such as fluorescence, type IIa, or type IIb diamonds. Color machines have the advantage of producing consistent and reliable results, without the impact of human judgement or fatigue. They work by measuring the wavelength of light moving through the stone. When a stone is subjected to ultraviolet light, the stone absorbs some light, and some is transmitted through it. Different wavelengths correspond to different colors of the rainbow, and color machines can identify these very subtle differences in wavelength, and classify them based on color ranges for diamonds. However, these machines cannot replace human judgment, and exist only to provide a second opinion. There are certain types of stones that do not respond well to color machines, and fluorescence is known to cause misleading results. Interestingly, certain rough productions, such as those hailing from Brazil and Sierra Leone, have structural compositions that often give misleading results from even the most advanced color machines on the market.
Anyone who has ever worked in the stock department of a rough sorting operation will know that counting diamonds is a challenging and often mundane task that is fraught with human errors, either deliberate or accidental. However, diamond counting is an important security and control requirement that can help to identify potential theft or control problems. Historically, this was a manual task that could add extra days to a rough production cycle. Machines now exist that make the process of counting stones both accurate and repeatable. Machines such as the Diamond Count made by Israel based Data Technologies work by funneling stones across a beam of light. Every time the light beam is interrupted, the machine registers a counted stone. Machines like this can count stones as small as 0.5 mm at up to 3,000 stones per minute, depending on size.
Although rough planning machines are a staple of the manufacturing industry, rough sorters also use them, mostly on larger or more complicated diamonds. These machines allow the user to identify potential polished diamond outcomes, and to therefore place an accurate value on the stone for sale. There are many such machines on the market today, and more advanced technology seems to appear frequently. These machines rely on 3D imaging sensors that reconstruct pictures of the stone into a three dimensional model, including internal characteristics. Most can detect impurities down to just one or two microns in size. With the aid of software, the user can plot different polished diamond scenarios to maximize the value of the final finished diamond. These machines come in portable versions that can fit inside a briefcase, allowing rough diamond buyers to evaluate stones in any location.
Diamond management software is a critical piece of any rough sorting operation to manage and control diamond stock. The old days of controlling diamond stock using paper reports and 'chits' are long gone. Industry leaders, such as the 'Fantasy' system by Rubenstein Software or 'DiamondXecutive Pro' by Aerodiam, complement other in-house built software platforms used by rough producers. These systems help to manage the complex rough sorting parameters of producers, who often have in excess of 10,000 individual diamond classifications.
Automatic sorting machines have advanced dramatically over the last few years, and many rough producers use these machines exclusively to sort small melee goods. This has helped to significantly reduce the amount of human sorting work required in larger operations. While some automatic sorters exist on the market for anyone to purchase, most large companies have developed their own internal technologies, or customized off-the-shelf equipment. Rough producers often employ several different types of sorting machines that separate stones based on different characteristics like size, shape, quality, and color.