Iolite is the gem-quality blue or blue-violet variety of cordierite. While iolite enjoyed popularity in jewelry in 18th-century Europe, this naturally beautiful gemstone is relatively new to the jewelry market and is regaining popularity with the public. Because of its hardness and pleochroism, iolite is one of the most difficult stones to cut. It must be cut in a certain direction to take advantage of the best color, which can be tough when the shape of the rough doesn't lend itself to cutting in that same direction.
|Iolite should not be cleaned in ultrasonic or steam cleaners. It is safe to clean iolite with warm soapy water, but avoid abrupt changes in temperature.|
|Iolite is typically light to dark blue or violet-blue, but it may also occur in light shades of yellow, green, gray, or brown. Violet-blue iolite is considered ideal color. Iolite is strongly trichroic, meaning that it shows three colors when viewed from different angles. A cube-shaped piece of iolite can appear blue from one angle, clear from another, and surprisingly golden from another. |
|Most colored stones are valued first and foremost on the intensity and saturation of their color. Iolite is no exception, but there is a caveat. Like blue sapphire, there's a narrow range of tones in which iolite's rich blue displays at its best. Otherwise, iolite's purplish-blue hues can cross the line into "inky" territory, making the stone overdark and lifeless or, in the worst cases, appear black.|
Name Origin and Meaning
The name "iolite" is derived from the Greek word ios, meaning "violet," as well as dichroite, Greek for "two-colored rock" and the root of the word dichroic, meaning a gem that displays two colors. Yet another name sometimes used to refer to iolite is its species name, cordierite, which was officially named in 1813 after French geologist Pierre L. A. Cordier, the man who first described it in 1809. Iolite had been discovered and used in jewelry in Sri Lanka (Ceylon) long before that, however.
In rare cases, some iolite gems can display one of three optical properties known as phenomenon: a star (asterism) or a cat's-eye effect (chatoyancy) when cut en cabochon, or aventurescence, which is a glittering effect caused by light reflections playing off of small plate-like inclusions in the stone. The inclusions can be a variety of materials; "bloodshot iolite" is a trade name given to aventurescent iolite that contains tiny hematite inclusions.
Have you ever noticed how deep bodies of water sometimes look blue, but that same water looks clear in shallow depths or from different angles? Pleochroic iolite is much like water in that case--it looks blue from one angle and can look completely clear from another. Perhaps this is why iolite has also been called "water sapphire," though it's not related to sapphire at all.
Iolite is sometimes referred to as "the Viking stone" because, according to Norse legend, Vikings used thin slices of iolite as polarizing filters, allowing them to look directly at the sun and use its exact location in the sky to navigate the open seas. If this is true, it would help explain how the Vikings supposedly managed to travel such great distances across massive expanses of ocean without modern navigational aides.
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