Hardness 7-7.5 specific gravity 2.6
Refractive index 1.54-1.57 birefringence 0.008
Wear: good durability, avoid impact
"Iolite" is a kind of very obvious "polychromatic" gem. When viewed from different angles, it will show different colors from blue, purple to yellow. It is a very magical gem. However, due to the strong polychromism, it also affects the color purity of the gem.
Cordierite is a kind of magnesium aluminum silicate. Its chemical composition is Mg2Al3 (alsi5o18). It belongs to orthorhombic system. There are few Gem Crystals with complete crystal faces in nature. Most of the raw cordierite mined are in damaged state.
Cordierite is a September Birthstone.
The history of human understanding of cordierite
The English name "Iolite" of "cordierite" comes from the Greek word "violet". Another ancient name of this kind of gem is "dichroite", which means "two colors of stone". Cordierite also has another name of "water sapphire", because its color is similar to "Sapphire".
"Cordierite" was once called "Vikings' compass" - it is said that Vikings used cordierite to judge the orientation of the sun in cloudy days - cordierite crystal presents different colors at different angles of polarized light transmission, so it can be traced to find the light source, that is, the direction of the sun.
Cordierite is named cordierite in honor of Louis Cordier, the French geologist and gemologist who first recorded the mineral in 1813. He is also one of the founders of the French Geological Association.
Production and origin of cordierite
Cordierite is mainly produced in gneiss or volcanic rocks, and it is produced all over the world, such as Madagascar, Sri Lanka, Germany, Brazil, Zimbabwe, India, Myanmar and the United States. In addition, the production of Norway is also the reason for the Vikings to obtain the gem.
Factors influencing the value of cordierite
The most valuable colors of "cordierite" are "blue" and "purple". However, the "polychrome" improves the difficulty of gemstone cutting. Gemstone cutters need to find the best cutting angle, which can not only present the beauty of polychrome, but also retain the color of the gemstone itself.
The polychromatic range of blue cordierite is from colorless to yellow, bluish gray and dark violet, which may be completely colorless at a specific observation angle.
The color of cordierite can't be changed by heating and other ways. Generally speaking, there is no treatment.
The common size of cordierite is 1-10ct, and high-quality gemstones over 5CT are relatively rare.
Wearing and preservation of cordierite
Cordierite is a kind of gemstone with good durability. Its hardness is above 7, but its toughness is poor and fragile. It should be worn to avoid impact. The best way to clean is warm soapy water