Staurolite
Species
Uncommon · Fe₂²⁺Al₉O₆(SiO₄)₄(O,OH)₂
Forms penetration twins in characteristic cross shapes at about 60 or 90 degrees, the 60 degree ones being the commoner. Found in medium-grade metamorphic schists alongside garnet and kyanite. Used as an indicator of moderate metamorphic pressure and temperature.
Identity
- Formula
- Fe₂²⁺Al₉O₆(SiO₄)₄(O,OH)₂
- Chemical class
- Silicate
- Also known as
- Fairy cross (cross-shaped twins), Fairy stone
Crystallography
- Crystal system
- Monoclinic
- Habits
- Prismatic
- Fracture
- Subconchoidal
Physical properties
- Mohs hardness
- 7
- Density
- 3.74 g/cm³
- Luster
- Vitreous, Resinous
- Colors
- reddish brown, dark brown, brownish black
- Streak
- white to gray
- Transparency
- Opaque, Translucent
Geology
- Origins
- Metamorphic
- Host rocks
- Schist and gneiss
- Associated minerals
- Kyanite, Garnet, Mica, Quartz
- Geography
- USA, Russia, France, Switzerland, Brazil
Classification
- Rarity
- Uncommon
- Gem quality
- No
Arcane properties
- Affinity
- Earth, Light
- Effects
- Warding
- Planar origin
- Material Plane
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Staurolite. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Staurolite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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