Burtite mineral
Calcium hexahydroxostannate mineral of the wickmanite group with current September 2026 IMA-CNMNC approved formula CaSn(OH)6, status A, and approval number IMA 1980-078. Sonnet (1981) described the type specimen (deposited at the Laboratoire de Mineralogie et de Geologie Appliquee, Universite catholique de Louvain, Louvain-la-Neuve, Belgium) from a tin-rich garnetite skarn (composed of 80% zoned andradite averaging 3.5 wt% SnO2 and 20% clinopyroxene) in the cliffs of the west bank of the river Beht near the El Hamman fluorite deposit (33 deg 31 min 26 sec Long., 5 deg 49 min 50 sec Lat.), 40 km southwest of Meknes, central Morocco, where it crystallized as a late hydrothermal phase replaced along rims by pale-yellow varlamoffite and associated with wickmanite, stokesite, datolite, pectolite, apophyllite, malayaite, and lollingite. CAMEBAX electron-microprobe analysis (mean of 14 point analyses on 5 fragments from 3 crystals, Table 1, p. 399) with stoichiometric H2O calculated for 6 OH groups yielded SnO2 56.3 (range 55.7-57.2), CaO 20.6 (20.3-20.9), MgO 0.3 (0.3-0.5), anhydrous sum 77.2 wt%, plus H2O 20.2 wt% (calc) and 2.6 wt% excess water by difference, corresponding on the basis of 6 OH groups to the empirical formula (Ca0.982Mg0.020)Sigma1.002Sn0.999(OH)6. Gandolfi powder and Weissenberg/precession single-crystal X-ray diffraction (Table 3, p. 400) index on a pseudo-cubic Pn3 or Pn3m unit cell with a = 8.128(1) A, Z = 4, Dmeas = 3.28(1) g/cm3, and Dcalc = 3.22 g/cm3, whereas uniaxial positive optics (nmeas = 1.633(1), ncalc = 1.630, birefringence < 0.0003) and diagonal extinction across {100} cleavage twin domains indicate true rhombohedral symmetry in space group R-3 (a_rh = 8.128 A, alpha ~ 90 degrees; hexagonal cell a = 11.49, c = 14.08 A). Burtite has Mohs hardness ~3 and dissolves slowly in cold dilute HCl. Distinct from wickmanite (MnSn(OH)6), schoenfliesite (MgSn(OH)6), natanite, and elemental tin; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.
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Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| IMA |
IMA:1980-078
|
Burtite |
Sources & References
-
ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 33, Burtite row: formula CaSn(OH)6, status A, IMA No. 1980-078, country Morocco, reference Canadian Mineralogist 19 (1981), 397; column definitions on PDF page 1.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-23) -
sonnet_1981_burtite: Sonnet PM (1981), Burtite, calcium hexahydroxostannate, a new mineral from El Hamman, central Morocco, Canadian Mineralogist 19:397-401. Complete 5-page primary PDF visually inspected: El Hamman tin-rich garnetite skarn occurrence and paragenesis pp. 397-399; CAMEBAX microprobe composition Table 1 p. 399; optical properties, twinning, rhombohedral R-3 vs pseudo-cubic Pn3/Pn3m crystallography, and powder XRD Tables 2-3 pp. 399-400.
https://www.rruff.net/doclib/cm/vol19/CM19_397.pdf (accessed 2026-10-23)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-23T07:15:00Z |
antigravity | CREATE | Created burtite mineral record with verified IMA:1980-078 identity, El Hamman skarn microprobe chemistry, and pseudo-cubic/rhombohedral R-3 wickmanite-group crystallography from the complete 1981 primary study. |
Record source: data/records/burtite.yaml