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| Fluor-liddicoatite | |
|---|---|
 Liddicoatite from the Ambesabora pegmatite, Madagascar. Photo Rob Lavinsky | |
| General | |
| Category | Cyclosilicate Tourmaline Group |
| Formula (repeating unit) | Ca(Li2Al)Al6(BO3)3Si6O18(OH)3F |
| IMA symbol | Fld[1] |
| Strunz classification | 9.CK.05 (10 ed) 8/E.19-80 (8 ed) |
| Dana classification | 61.3.1.2 |
| Crystal system | Trigonal |
| Crystal class | Ditrigonal pyramidal (3m) (same H-M symbol) |
| Space group | R3m |
| Identification | |
| Formula mass | 945.8 g/mol |
| Color | Usually smoky brown, but also pink, red, green, blue, or rarely white. |
| Crystal habit | Stout prismatic, with a curved convex trigonal outline |
| Cleavage | Poor or absent on {0001}[2] |
| Fracture | Uneven to conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 7+1⁄2 |
| Luster | Vitreous |
| Streak | White to very light brown |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.02 |
| Optical properties | Uniaxial (−) |
| Refractive index | No = 1.637, Ne = 1.621 |
| Pleochroism | Strong: O dark brown or pink, E light brown or pale pink |
| Other characteristics | Not fluorescent, not radioactive |
| References | [3][4][5][6] |
Fluor-liddicoatite[7] is a rare member of the tourmaline group of minerals, elbaite subgroup, and the theoretical calcium endmember of the elbaite-fluor-liddicoatite series; the pure end-member has not yet been found in nature.[3] Fluor-liddicoatite is indistinguishable from elbaite by X-ray diffraction techniques. It forms a series with elbaite and probably also with olenite.[3] Liddiocoatite is currently a non-approved mineral name, but Aurisicchio et al. (1999) and Breaks et al. (2008) found OH-dominant species.[8][9] Formulae are
- Fluor-liddicoatite Ca(Li2Al)Al6(BO3)3Si6O18(OH)3F
- Elbaite Na(Al1.5Li1.5)Al6(BO3)3Si6O18(OH)4
- Olenite NaAl9B3Si6O27O3(OH)
Fluor-liddicoatite was named in 1977 after Richard T. Liddicoat (1918–2002) gemmologist and president of the Gemological Institute of America,[2] who is well known for introducing the GIA diamond grading system in 1953.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b American Mineralogist (1977) 62:1121
- ^ a b c Gaines et al (1997) Dana’s New Mineralogy. Wiley
- ^ "Liddicoatite". www.mindat.org.
- ^ "Liddicoatite Mineral Data". www.webmineral.com.
- ^ "Liddicoatite" (PDF). University of Arizona. Mineral Data Publishing. 2001. Archived (PDF) from the original on 2006-09-05.
- ^ Darrell J. Henry; Milan Novák; Frank C. Hawthorne; Andreas Ertl; Barbara L. Dutrow; Pavel Uher; Federico Pezzotta (2011). "Nomenclature of the tourmaline-supergroup minerals" (PDF). American Mineralogist. 96 (5–6): 895–913. Bibcode:2011AmMin..96..895H. doi:10.2138/am.2011.3636. S2CID 38696645. Archived from the original (PDF) on 2012-03-26. Retrieved 2012-04-18.
- ^ Aurisicchio, C., Demartin, F., Ottolini, L. & Pezzotta, F. (1999). "Homogeneous liddicoatite from Madagascar. A possible reference material? First EMPA, SIMS, and SREF data". European Journal of Mineralogy. 11 (2): 237–242. Bibcode:1999EJMin..11..237A. doi:10.1127/ejm/11/2/0237.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Breaks, F.W.; Tindle, A.G. & Selway, J.B. (2008). Electron microprobe and bulk rock and mineral compositions from rare-element pegmatites and peraluminous, S-type granitic rocks from the Fort Hope pegmatite field, north-central Superior Province of Ontario. Vol. 235. Ontario Geological Survey, Miscellaneous Release Data.