Found in every color except red, sapphires are corundums that are colored by different impurities. Whether colored by iron and titanium to create blue sapphires, chromium for pink sapphires, or iron for yellow or green sapphires, the popularity and rarity of sapphires have become second to diamonds for engagement rings.
When purchasing sapphires, the most important quality to look for is color followed by cut and clarity. When judging a stone for color, one would want to make sure that it has the darkest color possible. To get an accurate reading on the color, one should always look at the color along the edge of the stone and not straight down the middle. Other color concepts to be aware of when buying sapphires or any gemstones are color zones and color bands. Color zones are areas of the gemstone that have a lighter or darker color then the general color of the stone. Color bands are streaks of dark or light colors that run through the gemstone.
The next important concept when buying a good quality sapphire is the cut of the stone. Cut is important because it brings out the color of a sapphire and the more color that it displays, the more beauty and value the sapphire will have. There are three important factors when it comes to cut: symmetry, polish, and windowing. Symmetry is the easiest when determining the quality of sapphire because one should observe along the outline of the gemstone to see if it is of symmetrical shape. One should also study the sapphire while rotating it three hundred and sixty degrees to see if the facet junctions are lined up. Next, under an overhead light, one should look at the surface of the sapphire. The presence of little lines appearing like scuff marks signifies wheel marks from the polishing phase. The presence of these marks takes away from the beauty and value of the stone. Windowing simply means that one can look through the top of a gemstone and see right through to the bottom.
The final factor when buying a sapphire is clarity. Clarity is always the last thing to look at when evaluating whether a gemstone is worth buying. Impurities in gemstones cause color and usually with these impurities you will have inclusions or flaws within the stone. Sapphires are a category 2 gemstone; meaning that these gemstones will have some inclusions but not enough to take away from the beauty of the gemstone. When observing the clarity inside a sapphire, one should use a 10x loupe and a flashlight for dark field illumination which is transmitted light from either the side or behind the gemstone. When observing the surface of a tanzanite for any imperfections, one should use a 10x loupe and an overhead light.
Hydrothermal, Chatham, pulled, and flame fusion are the synthetic sapphires that are on the market today. There are many indicators that separate these man made works of art from the naturals. With hydrothermal, there will be color bands that are parallel to each other, Chatham sapphires will have gas bubbles, pulled will be totally clean of inclusions, and flame fusion with star sapphires will have gas bubbles.
Treatments of gemstones are another process that sapphires face in today’s market. With the high demand of quality gemstones today, the industry would not be able to keep up with consumer needs without treatments. The treatments that sapphires are subject to are diffusion, bulk diffusion, and heating. Heat treatment is used to enhance the color of the sapphire and is the most popular treatment. Diffusion is the process of coating poor sapphires with cobalt, and bulk diffusion is the process of putting poor sapphires in a kiln with chrysoberyl until the beryllium is released from the chrysoberyl and penetrates the surface of the sapphires. Luckily, these treatments are easy to identify by placing the sapphire in a cup filled with some water. If diffusion or bulk diffusion was used on a sapphire, it will display color saturation on the facet junctions when placed in water.
Whether treated or untreated, synthetic or natural, sapphires have been a popular choice in jewelry for centuries and are just as popular today.