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Staurolite

Staurolite

Iron Aluminum Silicate Hydroxide
Fe2Al9Si4O22(OH)2

A special property of staurolite is that it often occurs twinned in a characteristic cross-shape.

The History Says
Staurolite was the regional metamorphic mineral of Greek from intermediate to high grade. From Greek the name has been derived. There 'stauros' mean cross, as is referred to the common twinning of the mineral.

The Present Scenario
Staurolite is the official state mineral of Georgia.


Staurolite is a common metamorphic mineral, being useful to geologists in determining the degree of metamorphism. It is famous because of its twinned crystals which forms the shape of a cross. The name has been derived from Greek word "stauros," which mean a cross.

The twin is a classic penetration twin. It appears like two crystals grew into and out of each other. In fact, it forms two twin types. One of them is nearly 90 degrees and the other, nearly 60 degrees. The most sought and common is the 60 degree type.

It was associated with Christianity, for the symbol cross and as a good luck charm. It is also called "Fairy Stone" or "Fairy Cross." Some of the scarcer specimens show both the twin forms and can really look like a blunt six rayed star.

Physical Properties of Staurolite

Color Reddish-brown, brown, and black.
Luster Vitreous to resinous to dull.
Transparency Crystals are translucent to opaque.
Crystal system Monoclinic, 2/m
Crystal habits Prismatic or tabular. Some may have a psuedo-hexagonal cross-section but most of them are flattened into a more (+) or X-shaped and can be both at the same time. Crystals are sometimes grown onto kyanite crystals.
Cleavage Poor, in one direction.
Fracture Uneven to conchoidal.
Hardness 7 - 7.5
Specific gravity 3.7 - 3.8
Streak White

Associated Minerals of Staurolite

  • Almandine
  • Micas
  • Kyanite
  • Other metamorphic minerals

Occurrences of Staurolite

  • Ducktown Tennessee, Georgia, Virginia and Montana, USA
  • Brazil
  • Scotland
  • Italy
  • France











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