Knowledge
28.02.2022 Sapphire varieties – more than just blue
Like rubies, sapphires belong to the corundum group. They are 9 on the Mohs scale of hardness, making them the hardest minerals in the world after diamonds. The best known are blue sapphires, sapphires with other colors are called “fancy sapphires”.
The best-known varieties are pink, orange, yellow and white sapphires, but there are also bi-color, color-change and star sapphires. Since colored sapphires are generally rare, particularly desirable colors such as pink are also artificially produced by heating.
Blue sapphires – royal sapphires
The best-known color variety is blue sapphire, the name is also derived from the Greek term for “blue”. Deep blue sapphires, also called royal blue sapphires, are the most sought after. The blue coloration is created by the interaction of titanium oxide and iron in the stone.
Pink Sapphires
Pink sapphires exist in different shades of color from a soft pink to a strong pink with violet nuances. There are also stones with red nuances, although these are rarer. Stones with violet nuances, found mainly in Madagascar, are fired at low temperatures to obtain pink sapphires. Besides Padparadscha sapphires, pink ones are currently the most desired ones after blue sapphires and fetch the highest prices.
Padparadscha sapphires – the color of the lotus flower
The Padparadscha is orange-pink, the name comes from Sanskrit or Sinhalese, where “padma raga” means “lotus colored”. In the past, many stones with a color shade between orange and pink were called padparadscha, but nowadays gemological laboratories restrict this name to a narrow color range of pink-orange or orange-pink. If the color saturation is less strong, the sapphires are called peach-colored. Padparadscha sapphire is the only gemstone in which the value increases as the color saturation decreases.
Yellow sapphires
This color variety is caused by the iron contained in the stone. These stones can also fetch good prices, but must be of very high quality to do so. Yellow sapphires are mainly used for jewelry.
White or colorless sapphires
White or colorless sapphires are the purest form of corundum. They are relatively rare compared to other color varieties and are valued in jewelry making as an alternative to diamonds.The lack of color is due to the fact that this variety does not contain foreign metal ions.
Sapphires with effects – star sapphires, color change and bicolor sapphires
The so-called star sapphires show an asterism: rutile inclusions give the impression of a star. To emphasize the star phenomenon, star sapphires are usually cut as cabochons. One of the most famous star sapphires is the “Star of Bombay,” which is 182 carats.
Color-changing sapphires show a different color under fluorescent light; for example, they appear violet in natural light and blue under UV light. The intensity of the color change varies depending on the stone and can range from a faint glimmer to two clearly distinguishable colors. The more visible and the more pronounced the color change, the more expensive the stone. Color change sapphires come in shades of blue, purple and brown.
Bicolor sapphires are stones in which the two colors or color zones are visible to the naked eye in natural light. They are also called Parti sapphires and can be brown and yellow or green and blue. The most desirable stones are those that show a gradual change, with one color variety occurring at one end of the stone and the coloration ending with the other color variety at the other end. These sapphires are rare compared to other fancy sapphires.
Dr. Thomas Schröck
The founder and managing partner of THE NATURAL GEM has been active in international gemstone trading for 30 years. As a doctor of economics and a certified gemmologist in Switzerland, Germany and the USA, among other countries, he is one of Europe’s leading experts on naturally-coloured, untreated gemstones and investments in them.
