mineral
Black kyanite
Kyanite, Al₂SiO₅
AI-generated identification · may be incorrectDark gray to black, elongated bladed crystals with a pearly to vitreous luster and perfect cleavage. Hardness is strongly directional: about 4.5–5 parallel to the blade and 6.5–7 across it; triclinic crystal system.
Identified More mineral →
Explore Black kyanite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, elongated bladed crystals with a pearly to vitreous luster and perfect cleavage. Hardness is strongly directional: about 4.5–5 parallel to the blade and 6.5–7 across it; triclinic crystal system.
Formation & geological history
Forms during regional metamorphism of aluminum-rich rocks, commonly in schist and gneiss; crystals may be millions to billions of years old. This specimen’s bladed form and dark color are consistent with kyanite.
Uses & applications
Used chiefly as a high-temperature refractory material; attractive specimens are collected and occasionally fashioned into jewelry.
Geological facts
Kyanite’s unusual direction-dependent hardness is diagnostic among common minerals with the same chemical formula as andalusite and sillimanite.
Field identification & locations
Look for flattened, lengthwise-striated blades and test hardness in different directions; common sources include Brazil, Nepal, India, and the United States. Identification from appearance alone is not definitive.
More like this
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
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Unidentified pink-and-gray mineral or rock specimen
Undetermined; the image is too blurry for reliable identification
mineral