TY - JOUR
T1 - Lavinskyite, K(LiCu)Cu6(Si4O11) 2(OH)4, isotypic with plancheite, a new mineral from the Wessels mine, Kalahari Manganese Fields, South Africa
AU - Yang, Hexiong
AU - Downs, Robert T.
AU - Evans, Stanley H.
AU - Pinch, William W.
N1 - Funding Information:
This study was funded by the Science Foundation Arizona.
PY - 2014/2
Y1 - 2014/2
N2 - A new mineral species, lavinskyite, ideally K(LiCu2+)Cu 62+(Si4O11)2(OH) 4 (IMA 2012-028), has been found in the Wessels mine, Kalahari Manganese Fields, Northern Cape Province, South Africa. Associated minerals include wesselsite, pectolite, richterite, sugilite, and scottyite. Lavinskyite crystals are tabular [parallel to (010)]. The mineral is light blue, transparent with very pale blue streak and vitreous luster. It is brittle and has a Mohs hardness of 5; cleavage is perfect on {010} and no parting was observed. The measured and calculated densities are 3.61(3) and 3.62 g/cm3, respectively. Optically, lavinskyite is biaxial (+), with α = 1.675(1), β = 1.686(1), γ = 1.715(1), 2Vmeas = 64(2) . An electron microprobe analysis produced an average composition (wt%) of SiO2 42.85(10), CuO 46.13(23), K2O 4.16(2), MgO 1.53(17), Na2O 0.27(4), BaO 0.18(6), and MnO 0.08(1), plus Li2O 1.38 from the LA-ICP-MS measurement and H2O 3.22 (added to bring the analytical total close to 100%), yielding a total of 99.79% and an empirical chemical formula (K0.99Ba0.01)Σ=1.00(Li 1.04Cu0.93Na0.10)Σ=2.07 (Cu5.57Mg0.43Mn0.01) Σ=6.01(Si4.00O11)2(OH) 4. Lavinskyite is isotypic with plancheite, Cu8(Si 4O11)2(OH)4·H2O, an amphibole derivative. It is orthorhombic, with space group Pcnband unit-cell parameters α = 19.046(2), β = 20.377(2), γ = 5.2497(6) Å, and V = 2037.4(4) Å3. The key difference between lavinskyite and plancheite lies in the coupled substitution of K + and Li+ in the former for H2O and Cu 2+ in the latter, respectively. The structure of lavinskyite is characterized by the undulating, brucite-like layers consisting of three distinct octahedral sites occupied mainly by Cu. These layers are sandwiched by the amphibole-type double silicate chains extending along the c axis, forming a sheet structure of compact silicate-Cu-silicate triple layers. Adjacent sheets are linked together by K and M4 (= Cu + Li) cations, as well as hydrogen bonding. The M4 site is split, with Cu and Li occupying two different sites. Lavinskyite exhibits more amphibole-like structural features than plancheite, as a consequence of K in the large cavity between the two back-to-back double silicate chains.
AB - A new mineral species, lavinskyite, ideally K(LiCu2+)Cu 62+(Si4O11)2(OH) 4 (IMA 2012-028), has been found in the Wessels mine, Kalahari Manganese Fields, Northern Cape Province, South Africa. Associated minerals include wesselsite, pectolite, richterite, sugilite, and scottyite. Lavinskyite crystals are tabular [parallel to (010)]. The mineral is light blue, transparent with very pale blue streak and vitreous luster. It is brittle and has a Mohs hardness of 5; cleavage is perfect on {010} and no parting was observed. The measured and calculated densities are 3.61(3) and 3.62 g/cm3, respectively. Optically, lavinskyite is biaxial (+), with α = 1.675(1), β = 1.686(1), γ = 1.715(1), 2Vmeas = 64(2) . An electron microprobe analysis produced an average composition (wt%) of SiO2 42.85(10), CuO 46.13(23), K2O 4.16(2), MgO 1.53(17), Na2O 0.27(4), BaO 0.18(6), and MnO 0.08(1), plus Li2O 1.38 from the LA-ICP-MS measurement and H2O 3.22 (added to bring the analytical total close to 100%), yielding a total of 99.79% and an empirical chemical formula (K0.99Ba0.01)Σ=1.00(Li 1.04Cu0.93Na0.10)Σ=2.07 (Cu5.57Mg0.43Mn0.01) Σ=6.01(Si4.00O11)2(OH) 4. Lavinskyite is isotypic with plancheite, Cu8(Si 4O11)2(OH)4·H2O, an amphibole derivative. It is orthorhombic, with space group Pcnband unit-cell parameters α = 19.046(2), β = 20.377(2), γ = 5.2497(6) Å, and V = 2037.4(4) Å3. The key difference between lavinskyite and plancheite lies in the coupled substitution of K + and Li+ in the former for H2O and Cu 2+ in the latter, respectively. The structure of lavinskyite is characterized by the undulating, brucite-like layers consisting of three distinct octahedral sites occupied mainly by Cu. These layers are sandwiched by the amphibole-type double silicate chains extending along the c axis, forming a sheet structure of compact silicate-Cu-silicate triple layers. Adjacent sheets are linked together by K and M4 (= Cu + Li) cations, as well as hydrogen bonding. The M4 site is split, with Cu and Li occupying two different sites. Lavinskyite exhibits more amphibole-like structural features than plancheite, as a consequence of K in the large cavity between the two back-to-back double silicate chains.
KW - K(LiCu)Cu6(Si4O11)2(OH)4
KW - Lavinskyite
KW - Raman spectra
KW - X-ray diffraction
KW - crystal structure
KW - plancheite
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U2 - 10.1515/am.2014.4601
DO - 10.1515/am.2014.4601
M3 - Article
AN - SCOPUS:84894581275
SN - 0003-004X
VL - 99
SP - 525
EP - 530
JO - American Mineralogist
JF - American Mineralogist
IS - 2-3
ER -