mineral
Iolite
Cordierite (Mg2Al4Si5O18)
AI-generated identification · may be incorrectMohs hardness 7 to 7.5, distinct blue to violet-blue pleochroism, vitreous luster, orthorhombic crystal system, poor cleavage, and specific gravity around 2.6.
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Physical properties
Mohs hardness 7 to 7.5, distinct blue to violet-blue pleochroism, vitreous luster, orthorhombic crystal system, poor cleavage, and specific gravity around 2.6.
Formation & geological history
Forms primarily through regional and contact metamorphism of argillaceous rocks, as well as in igneous granitic pegmatites.
Uses & applications
Frequently cut as a gemstone for jewelry and utilized as an optical filter due to its strong pleochroism.
Geological facts
Historically known as the Vikings' compass, navigators used thin slices of iolite to locate the sun on overcast days by observing polarization.
Field identification & locations
Identify by its characteristic water-sapphire appearance and distinct color shifts when viewed from different angles; found in India, Sri Lanka, Brazil, and Madagascar.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Granite
Granite (Phaneritic intrusive igneous rock)
igneous