Re-examination of holotype "clinoholmquistite", ideally (A)square Li-B(2) (C)(Mg3Al2) Si-T(8) O-22 (X)(OH)(2) (Ginzburg 1965) from the Tastyg spodumene deposit, Tuva, Siberia, Russia by EMP and SIMS analysis and structure refinement shows that the sample consists of a mixture of two distinct amphibole compositions, tremolite and a new amphibole end-member, fluoro-sodic-pedrizite, ideally Na-A Li-B(2) (C)(Mg2Al2Li) Si-T(8) O-22 F-X(2) (IMA-CNMMN 2004-002). Fluoro-sodic-pedrizite from Tastyg has the following crystal-chemical formula and unit-cell parameters: (A)(Na0.64K0.01) (B)(Li1.93Ca0.04Na0.03) (M1)(Mg1.69Fe0.312+) (M2)(Al1.98Cr0.01Zn0.01) (M3)(Li0.64Fe0.212+Mg0.13Mn0.02) (T1)(Si3.96Al0.04) (X)(F1.10OH0.90), a = 9.368(8), b = 17.616(10), and c = 5.271(4) angstrom, beta = 102.38(4)degrees, V = 849.6 angstrom(3), Z = 2. The structure has been refined to R-obs = 2.3% (I > 3 sigma 1) and R-all = 3.8%. Refined site-scattering values and site-geometries were used, together with EMP and SIMS results, to obtain site populations. Fluoro-sodic-pedrizite is the first amphibole end-member with dominant Li-C found in Fe-poor geologic environments. The coexisting tremolite contains only 0.002 wt% Li2O and 0.06 wt% B2O3, probably ordered at the T1 site. Crystal-chemical arguments, as well as preliminary experimental work, suggest clinoholmquistite is unstable.
Clinoholmquisite discredited: The new amphibole end-member fluoro-sodic-pedrizite.
Oberti R;Ottolini L
2005
Abstract
Re-examination of holotype "clinoholmquistite", ideally (A)square Li-B(2) (C)(Mg3Al2) Si-T(8) O-22 (X)(OH)(2) (Ginzburg 1965) from the Tastyg spodumene deposit, Tuva, Siberia, Russia by EMP and SIMS analysis and structure refinement shows that the sample consists of a mixture of two distinct amphibole compositions, tremolite and a new amphibole end-member, fluoro-sodic-pedrizite, ideally Na-A Li-B(2) (C)(Mg2Al2Li) Si-T(8) O-22 F-X(2) (IMA-CNMMN 2004-002). Fluoro-sodic-pedrizite from Tastyg has the following crystal-chemical formula and unit-cell parameters: (A)(Na0.64K0.01) (B)(Li1.93Ca0.04Na0.03) (M1)(Mg1.69Fe0.312+) (M2)(Al1.98Cr0.01Zn0.01) (M3)(Li0.64Fe0.212+Mg0.13Mn0.02) (T1)(Si3.96Al0.04) (X)(F1.10OH0.90), a = 9.368(8), b = 17.616(10), and c = 5.271(4) angstrom, beta = 102.38(4)degrees, V = 849.6 angstrom(3), Z = 2. The structure has been refined to R-obs = 2.3% (I > 3 sigma 1) and R-all = 3.8%. Refined site-scattering values and site-geometries were used, together with EMP and SIMS results, to obtain site populations. Fluoro-sodic-pedrizite is the first amphibole end-member with dominant Li-C found in Fe-poor geologic environments. The coexisting tremolite contains only 0.002 wt% Li2O and 0.06 wt% B2O3, probably ordered at the T1 site. Crystal-chemical arguments, as well as preliminary experimental work, suggest clinoholmquistite is unstable.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
