Corundum is the mineral species that includes both sapphire and ruby as varieties. Red corundum is known as ruby and all other coloured corundum (including colourless, or white sapphire as it is known in the trade) is sapphire.
Sapphire is generally known as a blue gemstone but surprisingly it comes in a wide range of colours and quality variations. In general, the more intense and uniform the colour is, the more valuable the stone.
Sapphires that are not blue are known as fancy sapphires, and may be any colour—except red (which is a ruby). The fancy sapphire colours are: pink, orange, yellow, green, purple, and violet. There truly is a different colour of sapphire to suit anyone’s taste.
In recent years, gemological labs have been asked to issue colour types on reports. This began with padparadscha sapphire, and has now spread to other varieties, including ruby and blue sapphire. What follows is the Gemology Guide to Colour Types.
Colour has the greatest influence on a sapphire’s value, and preferred sapphires have strong to vivid colour saturation. The most valued blue sapphires are velvety blue to violetish blue, in medium to medium-dark tones. At least 85% must be accounted by the primary colour of blue for a sapphire to termed blue. Sapphires with these qualities command the highest prices per carat. Less valuable blue sapphires might also be grayish, too light, or too dark.
Pastel. Sapphire does not just occur in high saturations, but also delicate pastel shades. Pastel blues come from Sri Lanka, Burma, Kashmir, Madagascar, Tanzania and Montana (USA).
Cornflower. Fine blue sapphires are often compared to the colour of the cornflower. Cornflower blues are typically found in the same places as pastel sapphires. In terms of tone and saturation, this colour lies between the lighter pastel blues and the deeper, more intense peacock and royal blues. Colour types cover a range, not just one specific colour. In the same as cornflowers can vary in their shades, can vary cornflower blue sapphires. The cornflower blue sapphire is mostly prized since finding a pure blue sapphire is extremely rare. This is the sapphire colour most sought after by the connoisseurs.
Peacock. In Sri Lanka, some of the finest blue sapphires have been compared with the colour of the neck or tail feathers of the peacock. This is an electric blue and can be quite spectacular.
Velvet. Velvet blue sapphires are among the most highly sought after by connoisseurs. Possessing a blue that is almost cobaltian in appearance, these sapphires hail mainly from Kashmir (India), Sri Lanka and Madagascar. "Milk of Magnesia" blue bottles are often compared with the colour of fine "velvet blue" type blue sapphires.
Royal. Of all the colours of ruby and sapphire, the royal blue is the most difficult to show on screen or in print, as the colour is out-of-gamut for both printing and most computer monitors. This is a vivid blue-violet with a deep tone and is epitomized by the fine sapphires from Burma's Mogok Stone Tract. In addition to Myanmar, royal blue sapphires are also found in Madagascar, Tanzania's Tunduru district, and in the smaller sizes, occasionally from Pailin (Cambodia) and Nigeria. Many large tanzanites display a royal blue colour.
Indigo. Indigo is a dye traditionally made from the indigo family of plants and is of ancient origin. Today it is seen most often as the blue colour of blue jeans. This colour type differs from the pure blues of cornflower, peacock, velvet and royal in that it is both deep in tone but slightly lower in saturation. Indigo sapphires are found in many places, particularly deposits derived from basalts. This includes Thailand, Madagascar, Australia, China and Nigeria, to name but a few.
Twilight. Resembling the deep blue colour of the sky a few minutes after sunset, twilight blue sapphires come from mainly basaltic sources, including Australia, Thailand, Cambodia, Nigeria, China and Vietnam.
The dividing line between pink sapphire and ruby has long been a point of dispute.
Pigeon's Blood. This colour type first appeared in English in 1839. It is said to be either of Chinese or Indian origin, but all agree that it is traditionally the term used to describe the finest colours of ruby. The vast majority of Mogok rubies tend towards purple. It is quite rare to have a stone that is a straight red. This is a glowing colour, not unlike that of a red traffic light. The pigeon's blood colour is not unique to Mogok; stones of this colour are also found at Mong Hsu (Burma), Vietnam, Mozambique, Tanzania and other localities.
Royal Red. A shade darker than pigeon's blood, this colour in Burma was traditionally called "rabbit's blood." These rubies tend to have a bit more iron than those of the pigeon's blood type. This cuts the fluorescence and blue transmission, making the stone a darker, pure red. Royal red rubies typically come from Mozambique, Thailand/Cambodia, Kenya and Madagascar.
Pink & Purple Sapphires
Pink sapphires range from light red (pink) to light purple with weak to intense colour saturation which fall out of the colour ranges for ruby or purple sapphire. Purple sapphires always have purple as the dominant colour. They range from medium to dark reddish purple to violetish purple with weak to vivid colour saturation. The major fancy sapphire colour categories are padparadscha, pink and purple, orange and yellow, green, and colourless and black. Each category has its own colour range, causes of colour, and market.
Lilac. Taking their name from the lilac flower, these sapphires feature a colour that varies from pastel lavender through rich violets. Lilac sapphires come to us mainly from Sri Lanka, Burma, Tanzania and Madagascar.
Hot Pink. Depending on one's opinion, this colour can fall into the pink sapphire or ruby category. What makes hot pink "hot" is the fact that these gems transmit more of the blue to violet wavelengths. This is due to a relatively low iron content relative to chromium. The result is a bit more bluish red and lots of fluorescence in the red. Gems displaying this colour typically come from low iron deposits. Virtually all of the Himalayan deposits (Tajikistan, Afghanistan, Pakistan, Nepal, Burma, Vietnam, Yunnan (China) can produce this color, as can some in East Africa (Mozambique, Tanzania).
Fuchsia. Named after the fuchsia flower, this is an intense purplish red, more red than hot pink.
Gems of this colour come from a variety of sources, including Burma, Sri Lanka,
Mozambique, Vietnam, Afghanistan and Tanzania.
Padparadscha. An extremely rare and collectible variety that is a mix of pink and orange is known in the trade as padparadscha. Some people say padparadscha sapphire colours should be called salmon or sunset. But the word padparadscha itself derives from the Sanskrit language and refers to the rich colour of a lotus blossom. The lovely padparadscha is the most valuable sapphire next to blue. The original source was Sri Lanka, but fine stones are also found in Madagascar, Tanzania and Vietnam.
Yellow to Orange Sapphires
Yellow sapphire is also available in a variety colour saturations from yellow to orangy yellow and in light to dark tones. The finest yellow sapphire is yellow to orangy yellow with vivid saturation.
Mekong Whisky. This colour of yellow sapphire is in high demand in the Thai market and takes its name from the local Mekong Whisky. These gems come mainly from Chanthaburi, Thailand. Heat-treated gems of a similar colour come from Sri Lanka.
Orange sapphires range from yellowish orange to reddish orange. Orange sapphires have deep golden, to mandarin, and deep orange colours. The finest orange sapphires are strong, pure orange to red-orange with medium tone and vivid saturation.
Commercial-grade sapphires may contain a less desirable greenish blue colour or strong greenish blue that is visible as you view the gem. Uniformly green sapphires that are saturated in colour are actually rare and many collectors prize them. In green sapphires, a mix of yellow and blue sapphire accounts for the colour a person sees.
Teal. An unusual variety of sapphire is the blue-green teal sapphire, taking its name from the teal duck. These generally come from basalt deposits, such as Australia, Ethiopia, Madagascar, and Thailand.
Colour Change Sapphires
Colour-change sapphires are corundum’s chameleons—stones that change colour under different lighting. Under daylight equivalent (fluorescent or LED daylight-balanced) light, the typical colour-change sapphire’s basic colour ranges from blue to violet. Under incandescent light, it ranges from violetish purple to strongly reddish purple. Some rare colour-change sapphires change from green in daylight to reddish brown in incandescent light.
When gem experts judge colour-change sapphires, they describe the colour change as weak, moderate, or strong. The strength of the stone’s colour change is the most important quality factor affecting its value.
Star corundum can be red, pink, blue, black, gray, brown, purple, or yellow—practically every colour under the sun. The term “star sapphire” encompasses all colours of star corundum except red, which is called star ruby.