Iolite
bluepurple · Cordierite family
| Also known as | Cordierite (Cordierite family) |
|---|---|
| Colour | Blue, Purple, Green, Yellow |
| Mohs hardness | 7–7.5 |
| Lustre | Greasy or vitreous |
| Streak | White |
| Crystal system | Orthorhombic |
| Transparency | Transparent to translucent |
| Cleavage | Fair on {100}, poor on {001} and {010} |
| Fracture | Subconchoidal |
| Specific gravity | 2.57–2.66 |
What is Iolite?
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present, and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (Mg,Fe)2Al3(Si5AlO18) to (Fe,Mg)2Al3(Si5AlO18). A high-temperature polymorph exists, indialite, which is isostructural with beryl and has a random distribution of Al in the (Si,Al)6O18 rings. Cordierite is also synthesized and used in high temperature applications such as catalytic converters and pizza stones.
How to identify Iolite
- Lustre: Greasy or vitreous.
- Hardness: Mohs 7–7.5 — hard enough to scratch glass.
- Streak: White.
- Habit: Orthorhombic crystal system.
Iolite in different forms
Stones often confused with Iolite
Frequently asked questions
How hard is Iolite?
Iolite is Mohs 7–7.5 on the hardness scale.
What colour is Iolite?
Iolite is typically blue, purple, green, yellow (Blue, smoky blue, bluish violet; greenish, yellowish brown, gray; colorless to very pale blue in thin section in transmi).