History
Some crystals of staurolite grow as two prisms locked at right angles, making a near-perfect cross. That habit gave the mineral its name. It comes from the Greek stauros — cross — joined to lithos, stone.
The French naturalist Jean-Claude Delamétherie set the name down in 1792, in a survey of the mineral kingdom. A few years later the crystallographer René Just Haüy tried to rename it staurotide, but the older word had priority and stuck.
The crosses are a quirk of how the crystals join, an arrangement mineralogists call cruciform penetration twinning — two crystals interpenetrating to make a cross. The common form crosses at about 60°; the rarer, more prized form makes a square 90° cross.
Those right-angled crosses earned a folk name and a folk story. In Patrick County, Virginia, they are called fairy stones, and the place where they weather out of the rock is now Fairy Stone State Park. Local legend holds that the crosses are the petrified tears of fairies, wept on hearing of the death of Christ.
The cross shape gave the stones a long second life as charms. Carried as amulets, they were believed to ward off illness, shipwreck, and rabies. Well-formed twins are still set into pendants, and imitations sold under the same fairy cross name circulated alongside the real thing in the early twentieth century.
Industrial & practical applications
Staurolite has almost no large-scale industry behind it, but it does one industrial job well: it cleans metal. Crushed to a coarse sand, it is fired at a surface through a compressed-air nozzle, so the hard grains cut through paint, rust, and other coatings. The stripped metal is then ready for painting or welding in plant maintenance and construction work. Being a hard, inert mineral with properties close to garnet, it works as a blasting abrasive yet costs far less.
The sand is not mined for its own sake. It is separated out of heavy-mineral concentrate during the processing of mineral sands. There the staurolite comes up alongside the zircon and titanium minerals that are the real targets.
For most people staurolite shows up not as sand but as a cross. The cross-shaped twins are cut into cabochons and set into pendants, sold as collector pieces and good-luck fairy cross charms rather than as a serious gemstone.
Staurolite earns its keep most reliably in the lab, not the marketplace. It is one of the index minerals geologists use to read a rock's past. Its presence pins the temperature, depth, and pressure at which the rock was reshaped deep in the crust. In the United States it carries one civic honour: it is the state mineral of Georgia.
Where it forms, where it's found
- Geological setting
Amphibolite grade of regionally metamorphosed pelitic rocks.
Varieties
Physical
Optical
- Optical type
- Biaxial (+) · 2V measured = 88° · 2V calc = 84 – 88°
- Refractive index
- 1.736 – 1.762
- Surface relief
- High
- Principal indices
- nα 1.736 – 1.747 · nβ 1.74 – 1.754 · nγ 1.745 – 1.762
- Pleochroism
- Visible
X= colourless Y= pale yellow Z= golden yellow
- Dispersion
- r > v weak
Crystallography
- Space group
- C2/m
- Cell parameters
- a = 7.86 Å · b = 16.6 Å · c = 5.65 Å
- Cell angles
- β = 90.45 °
- Ratio a:b:c
- 1 : 2.112 : 0.719
- Z
- 2
- Morphology
Prismatic crystals
- Twinning
Commonly 60-degree twins on (231), may be cyclic. Less commonly 90-degree cruciform twins on (031). On (320) (very rare).
- Comment
Pseudo-orthorhombic
Chemical composition
- Impurities
- Ti
- Cr
- Mn
- Co
- Zn
- Li
- H2O
Synonyms
- Baseler Taufstein
- Croisette
- Fairy Stone
- Staurolita
- Staurotide
In other languages
- French
- Granatite · Lusakite · Pierre de croix · Schorl cruciforme · Staurolite · Staurotide
- German
- Basler Taufstein · Lusakit · Staurolith
- Spanish
- estaurolita
- Italian
- Staurolite
- Portuguese
- Estaurolita · estaurolite
- Japanese
- 十字石
- Chinese
- 十字石
- Traditional Chinese
- 十字石
- Russian
- люсакит · нордмаркит · ставролит
Classification
9.AF.30
- 9SilicatesClass
- 9.ANesosilicatesDivision
- 9.AFNesosilicates with additional anions; cations in [4], [5] and/or only [6] coordinationGroup
- 9.AF.30StauroliteSpecies
52.02.03.01
- 52Nesosilicates Insular Sio4 Groups and O, Oh, F, H2oClass
- 52.02Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordinationType
- 52.02.03— unnamed intermediate level —Group
- 52.02.03.01StauroliteSpecies
16.19.5
- 16Silicates Containing Aluminum and other MetalsClass
- 16.19Aluminosilicates of Fe and MgGroup
- 16.19.5StauroliteSpecies
Group, growth & confusion
Literature, links & citation
- 1797Haüy, R.J. (1797) Staurotide. J. Mines: 5: 545.
- 1810Klaproth, M. H. (1810) CLXXXII. Untersuchung des Stauroliths. In Beiträge zur chemischen Kenntniss der Mineralkörper Vol. 5. Rottmann. p.80-85.
- 1876Dana, E.S. (1876) On new twins of staurolite and pyrrhotite. American Journal of Science, Series 3: 11: 384-387.
- 1904Friedel, G. (1904) Étude sur les groupements cristallins. Extrait du Bulletin de la Société de l'Industrie minérale, Quatrième série, Tomes III et IV. Saint-Étienne, Société de l’Imprimerie Théolier J. Thomas et C..
- 1929Náray-Szabó, St. (1929) VII. The structure of staurolite. Zeitschrift für Kristallographie - Crystalline Materials, 71 (1). 103-116 doi:10.1524/zkri.1929.71.1.103DOI: 10.1524/zkri.1929.71.1.103
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Staurolite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/staurolite-3753},
note = {Accessed 2026-05-11}
}