Mineral Information and Data:

Mg2Al4Si5O18 [CNMNC approved formula]

Named after Pierre Louis A. Cordier (1777-1861), French mining engineer and geologist, who first studied this species.

IMA status : Valid species (Pre-IMA 1813) Grandfathered
(8th edition) :  
  (61) Cyclosilicate Six-Membered Rings
  (61.02) with Al substituted rings stitution
  (61.02.01) Cordierite group
(10th edition) :
  (09) Silicates
  (09.C) Cyclosilicates
  (09.CJ) [Si6O18]12- 6-membered single rings (sechser-Einfachringe), without insular complex anions
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 9.739 Å, b = 17.08 Å, c = 9.345 Å
Crystal Habit: Crystals short prismatic; massive, compact, embedded grains
Twinning: Common on {110} or {310}, simple, lamellar, or cyclic
Color: Blue, bluish violet, greenish, gray, yellowish, brown
Diaphaneity: Transparent to ranslucent
Luster: Vitreous
Hardness (Mohs): 7 to 7.5
Measured Density: 2.53 to 2.78 g/cm3
Cleavage: 3; {010} distinct, {001} and {100} indistinct
Tenacity: Brittle
Fracture: Sub-conchoidal
Streak: Colorless
Polymorphism and Series: Dimorphous with indialite. Forms a series with sekaninaite.
Geologic Setting: In thermally metamorphosed argillaceous sediments and high-grade regionally metamorphosed schists, gneisses, and granulites; in mafic igneous rocks and granites; detrital.
Mineral Association: Sillimanite, potassic feldspar, muscovite, biotite, corundum, spinel, garnet, andalusite
Synonyms/varieties: Agalmatolite (massive alteration), iolite (gem var.), pinite (alteration), water-sapphire
Other Properties: Gemstone Rare.


Cordierite in anhydrite with chalcopyrite
Origin: Ruttan Mine , Leaf Rapids, Manitoba, Canada
Sample size: 3.5 x 3.5 x 2.5 cm
Photo: Rob Lavinsky


(zoom-in of above)


Coarse grained quartz-cordierite segregations in biotite-anthophyllite rocks.
Origin: Bjordammen, Telemark, Norway
Sample size: 6 x 8 cm
Photo: Diederik Visser


coarse grained quartz-cordierite segregation with cordierite crystals up to one cm colored brown due to pinitisation
Origin: Bjordammen, Telemark, Norway
Sample size: 6 x 8 cm
Photo: Diederik Visser