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Staurolite
Current inventory:  0 gems
 

Staurolite

Chemistry:  (Fe2+;Mg)2Al9(Si;Al)4O20(O;OH)4
[Iron Aluminum Silicate Hydroxide]

Discovered in 1792;   IMA status: Valid (pre-IMA; Grandfathered).
Staurolite gets its name from the Greek words stauros and lithos, meaning stone cross.

 

Classification

   

   

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/B.03-10

Nickel-Strunz 10th Ed. ID:

9.GD.10

 

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination

Related to:

Staurolite Group. Staurolite - Gerstmannite Series

 

 

Crystal Data

   

   

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Commonly in prismatic crystals, typically rough, to 12 cm.

Twinning:

Commonly as 60 twins with [231] as twin plane, may be cyclic; less commonly as 90 cruciform twins with [031] as twin plane.

 

 

Physical Properties

   

 

Cleavage:

[010] Distinct

Fracture:

Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

7.0 - 7.5

Density:

3.74 - 3.83 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Dark Reddish Brown to Blackish Brown, Yellowish Brown, rarely Blue

Transparency:

Transparent to Opaque

Luster:

Sub-Vitreous to Resinous

Refractive Index:

1.736 - 1.762  Biaxial ( + )

Birefringence:

0.0090 - 0.0150

Dispersion:

Weak; r > v

Pleochroism:

Visible; X = colorless, Y = pale yellow, Z = golden yellow

 

 

Occurances

   

   

Geological Setting:

Common in pelitic schists, gneisses, and argillaceous rocks regionally metamorphosed to amphibolite grade; also a detrital mineral.

Common Associations:

Almandine, Chloritoid, Kyanite, Muscovite, Quartz, Sillimanite, Tourmaline

Common Impurities:

Ti, Cr, Mn, Co, Zn, Li, H2O

Type Locality:

n/a

Year Discovered:

1792

View mineral photos:

Staurolite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Staurolite is extremely rare as a faceted gem. The mineral forms in interesting crystals shaped like crosses or X's and are sometimes referred to as "Fairy Stone" or "Fairy Cross." Staurolite is famous for these "twinned" crystals that forms two twin types; one that is nearly 90 degrees (like a cross) and one that is nearly 60 degrees (like an X). The 60 degree type is more common but the 90 degree type is the most sought after as a symbol of the Christian cross and as a good luck charm. Some rare specimens show both twin forms together and look like a six rayed star. Transparent material is rarely found and cut gems are typically small and very dark red. They lack fire but are prized for their rarity.

Most facetable material comes from Ardenella and Rubellita, Minas Gerais, Brazil; Liaoning Province, China; and Pizzo Forno and Alpe Piona, Ticino, Switzerland.
 

  
Staurolite gems for sale:

We have not photographed our Staurolite gems. Please check back soon.
 

 

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