mineral
Iolite
Cordierite (Magnesium iron aluminium silicate)
AI-generated identification · may be incorrectHardness: 7-7.5 on Mohs scale; Color: Blue, violet-blue, smoky blue; Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.58-2.66
- Hardness
- 7-7
- Color
- Blue, violet-blue, smoky blue
- Luster
- Vitreous
Identified More mineral →
Explore Iolite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7-7.5 on Mohs scale; Color: Blue, violet-blue, smoky blue; Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: Good in one direction; Specific Gravity: 2.58-2.66
Formation & geological history
Formed through the regional or contact metamorphism of aluminous rocks. Commonly found in schists, gneisses, and certain types of contact metamorphic zones. Formed throughout geological time where tectonic pressures are present.
Uses & applications
Primarily used as a gemstone in jewelry, especially as a more affordable substitute for sapphire. Also used in industrial ceramics and catalyst supports because of its low thermal expansion.
Geological facts
Known as the "Viking's Compass" because it was allegedly used by Viking navigators to find the sun on cloudy days due to its extreme pleochroism—it changes color from blue to yellowish-gray when viewed from different angles.
Field identification & locations
Identify in the field by its distinct pleochroism (appearing different colors from different directions) and its tendency to look like a watery sapphire. Common locations include Sri Lanka, Myanmar, India, and Tanzania.
