Leakeite Root Name Group from
Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan
| Locality type: | Massif | |
| Classification | ||
|---|---|---|
| Species: | 'Leakeite Root Name Group' (not an IMA approved species) | |
| Formula: | ANa2(Z22+Z23+Li)(Si8O22)(OH,F,Cl)2 | |
| Formation: | Primary | |
| Comments: | Fairly abundant amphibole in the thin section (sample FKM-431), prior to analysis presumed to be arfvedsonite, occurs with abundant aegirine-augite, quartz, alkali feldspar, scattered leucosphenite and minor kupletskite-(Cs), in rare-element (Cs, Li, B)-rich granite. The sample was specifically acquired for leucosphenite. Ferri-leakeite had been originally recorded for the locality, but later it and the leakeite root-name species were declared "erroneously reported" due to not being mentioned in a particular reference; now the root-name group is re-confirmed by EPMA. Initial normalization to Si=8, prior to the inclusion of Li, yielded a cation deficiency at the C-site of almost exactly 1 apfu, an unreasonable Fe3+/∑Fe (>2.5 apfu), and a low total; all of these anomalous parameters indicated the presence of unanalyzed Li. Addition of roughly sufficient Li to fill the C-site deficiency yielded excellent totals and stoichiometries, using either normalization Si=8 or ∑cations = 16; normalized formulas reported here use the latter normaliztion scheme. The dominant species of the root-name group present appears to be ferro-ferri-leakeite, but there is less abundant lower "z" BSE-contrast zones that are more Mg- and F-rich and correspond to ferri-fluoro-leakeite. Even in the ferro-ferri-leakeite, F is high and is just barely under calculated OH, so local ferro-ferri-fluoro-leakeite is possible. Similarly, A-site K is fairly high and is also nearly equal to A-site Na, and indeed can be made exceed A-site Na by using a different normalization scheme that moves some A-site Na back to the M4-site, or by slightly adjusting the Li content to the same effect; hence, the local occurrence of various K-dominant species is also quite likely. Similarly again in the C-site, Mn2+ is significant and nearly exceeds Fe2+ in the dominant ferro-ferri-leakeite, so it may also be possible that locally a new named amphibole "mangano-ferri-leakeite" may be present (EDIT: in a second thin section (sample FKM-430) with a slightly different and more Mn-rich assemblage, an amphibole composition corresponding to "mangano-ferri-fluoro-leakeite" has been identified]. The choice of "leakeite root name group" then covers possible compositions potentially more enriched in K, F (or OH), and/or Mn (or Fe or Mg), relative to the dominant Na, OH (or F) and/or Fe (or Mn or Mg) combinations of the three so-far reported species, that may locally occur or be a determinable composition region within a zoned crystal. | |
| Confirmation | ||
| Validity: | Believed Valid | |
| Data | ||
| Mineral Data: | Click here to view Leakeite Root Name Group data | |
| Locality Data: | Click here to view Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan | |
| Data Identifiers | ||
| Mindat Occurrence Record ID: | 1590840 | |
| Long-form Identifier: | 1:3:1590840:5 | |
| GUID (UUID V4): | 6164b75e-2a04-48ab-b6bb-781d637f48a6 | |
| References | ||
Frank K. Mazdab collectionsample FKM-431; https://www.rockptx.com/fkm-426-to-fkm-450/#FKM-431 | ||
