Mineral Information and Data:

Andalusite
Al2OSiO4 [CNMNC approved formula]

Named after the type locality at the Ronda Massif, Málaga, Andalusia, Spain.

IMA status : Valid species (Pre-IMA 1798) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
52.02.02b.01  
  (52) Nesosilicate Insular SiO4 Groups and O, OH, F, and H2O
  (52.02) with cations in [4] and >[4] coordination
  (52.02.02b) AL2SIO5 (Andalusite subgroup)
  
Nickel-Strunz
(10th edition) :
09.AF.10
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AF) Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 7.79 Å, b = 7.90 Å, c = 5.56 Å
Crystal Habit: Blocky, equant, prismatic, euhedral crystals
Twinning: Rare on {101}
  
Color: Pink, reddish brown, rose-red, whitish
Diaphaneity: Transparent to nearly opaque with inclusions
Luster: Vitreous
Hardness (Mohs): 6.5 to 7.5
Measured Density: 3.13 to 3.16 g/cm3
Cleavage: 2; {110} distinct, {100} indistinct
Tenacity: Brittle
Fracture: Uneven to subconchoidal
Streak: White
  
Polymorphism and Series: Trimorphous with kyanite and sillimanite
Geologic Setting: A result of contact metamorphism of argillaceous sediments, also in regionally
metamorphosed schists. Rare in granites and pegmatites, which however a®ord the largest
crystals. Detrital in some sandstones.
Mineral Association: Kyanite, sillimanite, cordierite, corundum, garnet, tourmaline, mica
  
Synonyms/varieties: Apyre, chiastolite (cross-like patterned var.), gosseletite (Fe,Mn-rich var.), viridine (green, Fe3+ Mn-rich var.), manqanandalusite
Other Properties: Gemstone Readily Available.
Comments: Series with kanonaite.

 

Andalusite
Origin: Custer Co., South Dakota, USA
Sample size: 6 x 5 x 5 cm, crystal 4 x 2 x 2 cm
Photo: Tom Loomis

 

Andalusite
(zoom-in of above)

 

Andalusite
Manganoan andalusite (viridine)
Origin: Conquista, Bahia, Brazil
Sample size: 5 x 3 x 2.5 cm
Photo: Rob Lavinsky

 

Andalusite
(zoom-in of above)

 

Andalusite
Variety chiastolite
Origin: Lisental, Tyrol, Austria
Ex. Richard Hauck collection
Sample size: 8.3 x 6.5 x 5.1 cm

 

Andalusite
(zoom-in of above)

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