Mineral Information and Data:

Liddicoatite
Ca(Li2Al)Al6(BO3)3Si6O18(OH)3F [CNMNC approved formula]

Named for Richard T. Liddicot (1918-2003), gemologist, who invented the diamond grading system, for his many contributions to the Gemological Institute of America.

IMA status : Approved Species 1977 (IMA1976-041)
CLASSIFICATION 
Dana
(8th edition) :
61.03b.01.02  (This Dana# Changed)
  (61) Cyclosilicate Six-Membered Rings
  (61.03b) with borate groups (Calcic Tourmaline Subgroup)
  (61.03b.01) Liddicoatite Subgroup
  
Nickel-Strunz
(10th edition) :
09.CK.05
  (09) Silicates
  (09.C) Cyclosilicates
  (09.CK) [Si6O18]12- branched 6-membered single rings, with insular complex anions
  
Crystal system: Trigonal System
Point group (H-M): 3m — ditrigonal-pyramidal
Space group: R3m
Unit cell: a = 15.875(3) Å, c = 7.126(2) Å, Z=3
Crystal Habit: Crystals stout prismatic, with curved convex trigonal outline, deeply striated || [0001], to 25 cm.
  
Color: Brown, green, pink, red, blue; commonly zoned parallel to pyramid faces
Diaphaneity: Transparent to translucent
Luster: Vitreous on fractures
Hardness (Mohs): 7.5
Measured Density: 3.02 g/cm3
Cleavage: Poor on {0001}
Tenacity: Brittle
Fracture: Uneven to conchoidal
Streak: Very light brown
  
Geologic Setting: Detrital in soil, an apparent product of the local pegmatites.
Mineral Association: Quartz, elbaite, albite, micas
  
Other Properties: Gemstone Readily Available.

 

Liddicoatite
Origin: Antandrokomby, Manandona Valley ,Madagascar
Sample size: 2.4 x 2.2 x 1.4 cm
Photo: John Veevaert, Trinity Mineral Co.

 

Liddicoatite
(zoom-in of above)

 

Liddicoatite
(zoom-in of above)

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