| Name |  | Cordierite (Dichroite)
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| Chemistry |  | Mg2Al3[AlSi5O18] | 
| Hardness |  | 7 | 
| Lustre |  | greasy - vitreous | 
| Colour |  | colourless, grey, violet, blue, brown | 
| Streak |  | white | 
| Density [g/cm3] |  | 2.6 | 
| Crystal habit |  | orthorhombic, crystals
rarely, short columnar | 
| Cleavage, Fracture |  | fracture conchoidal | 
| other characteristics
and occurrences |  | iolite = blue violet
(gemstone variety) metamorphic mineral, primarily in gneiss
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