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Fluor-Liddicoatite (formerly Liddicoatite)
Current inventory:  1 gem
 

Liddicoatite

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

Discovered in 1976;   IMA status:  Valid (IMA approved: Redefined Approved 2011)

 

Chemistry

 

 

Chemical Formula:

Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3(OH)F

 

Calcium Lithium Aluminum Bora-silicate Hydroxide Fluoride Oxide

Molecular Weight:

917.49 gm

Composition:

Sodium

0.75 %

Na

1.01 %

Na2O

 

Lithium

1.21 %

Li

2.61 %

Li2O

 

Calcium

3.06 %

Ca

4.28 %

CaO

 

Aluminum

18.23 %

Al

34.45 %

Al2O3

 

Silicon

18.37 %

Si

39.29 %

SiO2

 

Boron

3.53 %

B

11.38 %

B2O3

 

Hydrogen

0.32 %

H

2.38 %

H2O

 

Oxygen

52.66 %

O

 

 

 

Fluorine

1.86 %

F

 

 

 

 

-  %

F

-0.78 %

-0=F2

 

 

100.00 %

 

96.95 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/E.19-80

Nickel-Strunz 10th Ed. ID:

9.CK.05

 

9 : SILICATES (Germanates)
C : Cyclosilicates
K : [Si
6O18]12- 6-membered single rings, with insular complex anions

Related to:

Tourmaline Group. The F-analogue of Liddicoatite.

Members of Group:

Tourmaline Group: Buergerite, Chromdravite, Chromo-aluminopovondraite, Dravite, Elbaite, Feruvite

Varieties:

None

Synonyms:

IMA1976-041

 

 

Crystal Data

   

   

Crystallography:

Trigonal - Ditrigonal Pyramidal

Crystal Habit:

Crystals stout prismatic, with curved convex trigonal outline, deeply striated || [0001], to 25 cm.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

Poor on {0001}

Fracture:

Irregular/Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.5

Density:

3.02 (g/cm3)

Luminescence:

Not Fluorescent

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Brown, Green, Pink, Red, Blue; commonly zoned parallel to pyramid faces.

Transparency:

Transparent to Translucent

Luster:

Vitreous on fractures

Refractive Index:

1.621 - 1.637  Uniaxial ( - ) 

Birefringence:

0.016

Dispersion:

n/a

Pleochroism:

Strong; O = dark brown; E = light brown

 

 

Occurances

   

   

Geological Setting:

Detrital in soil, an apparent product of the local pegmatites.

Common Associations:

Quartz, Elbaite, Albite, Micas

Common Impurities:

Mn, Fe, Ti, Mg, Na, H2O

Type Locality:

Near Antsirabé, Vakinankaratra Region, Antananarivo Province, Madagascar

Year Discovered:

1976 (Redefined Approved 2011)

View mineral photos:

Fluor-Liddicoatite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org (Fluor-Liddicoatite)
Mindat.org (Liddicoatite)
Webmineral.com (Liddicoatite)

 

 


Liddicoatite was originally thought to be Elbaite (Tourmaline) but upon further investigation it was discovered to be the calcium rich analog of Elbaite and in 1977 approved by the IMA as a new mineral. In 2011 Henry et al. determined that the material from the Type Locality is Fluorine (F) dominant instead of OH-dominant so the type material has been redefined as Fluor-Liddicoatite and "Liddicoatite" is currently a non-approved species name. I'm guessing most gem collectors will continue to call it Liddicoatite.

The only known locations for Fluor-Liddicoatite are Antsirabe, Tsilaizina, and Anjanabonoina, Madagascar. There are probably other localities but chemical analysis is required for distinction from other Tourmaline Group minerals. Liddicoatite is found in a wide variety of colors and crystals are often concentrically zoned or banded with many different colors, usually triangular in outline.
 

  
Liddicoatite gems for sale:

Liddicoatite-002

Gem:

Liddicoatite

Stock #:

LIDDI-002

Weight:

1.8840 ct

Size (w x d):

17.46 x 4.45 x 2.41 mm

Shape:

Long Emerald

Color:

Multi-color

Clarity:

SI2

Origin:

Madagascar

Treatment:

None (natural)

Price:

$160.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Liddicoatite-002

A very rare member of the Tourmaline family that is only found in Madagascar. This one is from Antsirabé, Madagascar. It has dark green, pink and colorless bands.


Liddicoatite-001

Gem:

Liddicoatite

Stock #:

LIDDI-001

Weight:

2.0020 ct

Size (w x d):

11.32 x 5.60 x 3.63 mm

Shape:

Emerald

Color:

Multi-color

Clarity:

HI

Origin:

Madagascar

Treatment:

None (natural)

Price:

SOLD

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Liddicoatite-001

A very rare member of the Tourmaline family that is only found in Madagascar. This one is from Antsirabé, Madagascar. It has dark green, pink and colorless bands.


 


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