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As iolite is very brittle and difficult for gem cutters to work with, high quality iolite gemstones are generally cut as a rectangular step-cut, with the table oriented to enhance the color. However lower-quality iolites with dark fibrous inclusions are often cut as cabochons.
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Chemical Formula | Magnesium aluminium silicate Mg2Al3 (AlSi5O18) |
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Color | Blue in various hues |
Hardness | 7-7.5 on Mohs Scale |
Crystal System | Orthorhombic; short prisms |
Refractive Index | 1.53-1.55 |
Cleavage |
imperfect |
Specific Gravity (SG) |
2.58-2.66 |
Transparency |
Transparent, translucent |
Fracture | conchoidal, uneven, brittle |
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