Levantite, KCa3(Al2Si3)O11(PO4), a new latiumite-group mineral from the pyrometamorphic rocks of the Hatrurim Basin, Negev Desert, Israel. (14th June 2019)

• Record Type: Journal Article
• Authors: Galuskin, Evgeny V.; Krüger, Biljana; Galuskina, Irina O.; Krüger, Hannes; Vapnik, Yevgeny; Pauluhn, Anuschka; Olieric, Vincent
• Is Part Of: Mineralogical magazine. Volume 83:Number 5(2019)
• Page Start: 713
• Page End: 721
• Publication Date: 2019-06-14
• Subjects: levantite, -- latiumite group, -- new minerals, -- Raman spectrum, -- pyrometamorphic rocks, -- Hatrurim Complex; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/mgm.2019.37
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: Levantite, with the end-member formula KCa3 (Al2 Si3 )O11 (PO4 ), is the phosphate analogue of latiumite, KCa3 (Al3 Si2 )O11 (SO4, CO3 ) found in gehlenite–wollastonite hornfels on Har Parsa, Negev Desert, Israel. Levantite forms later zones on long-prismatic crystals of latiumite. Rarer homogeneous colourless levantite crystals up to 0.2 mm long and with mean composition (K0.94 Ba0.01 Na0.01 □0.04 )Σ1.00 (Ca2.96 Mg0.03 )Σ2.99 {(Si2.69 Al2.06 Fe 3+ 0.16 P0.06 )Σ4.97 O11 }[(PO4 )0.65 (SO4 )0.35 ]Σ1.00 were noted. Minerals of the levantite–latiumite series are associated with gehlenite, wollastonite, clinopyroxene of the esseneite–diopside series, anorthite and Ti-bearing andradite. Levantite crystalises in space group P 21 with unit-cell parameters a = 12.1006(9) Å, b = 5.1103(4) Å, c = 10.8252(9) Å, β = 107.237(8)°, V = 639.34(9) Å 3 and Z = 2. The structure of levantite is analogous to latiumite. It is formed by tetrahedral hybrid zweier double layers [(Si, Al)10 O22 ] connected by Ca atoms. Three Ca atoms linked to different double layers are bridged over by (PO4 ) and minor (SO4 ) groups. K atoms reside in the cavities between two superimposed zweier double layers. The measured micro-indentation hardness of levantite gave VHN50 = 580(19) (mean of 14), range 550–611 kg/mm 2, which correlates with 5 on the Mohs scale. Cleavage is good on (100). Twinning on (100) is polysynthetic or simple. The calculated density is 2.957 g cm –3 . Levantite is optically negative with α = 1.608(2), β = 1.618(2), γ = 1.622(2) (λ = 589 nm), 2Vmeas. = 70(5)° and 2Vcalc. = 64.3°. Dispersion of the optical axes r > v is weak; the optical orientation is: Z = b, X ^ c = 22–27°; and it is non-pleochroic. Minerals of the levantite–latiumite series from Israel show characteristic Raman spectra with the main bands at 994 cm –1 [ν1 (SO4 ) 2– ] and 945 cm –1 [ν1 (PO4 ) 3– ]. The band intensity ν1 (PO4 ) 3– /ν1 (SO4 ) ratio is well correlated with P and S contents in the investigated minerals. The strongest lines in the powder diffraction pattern [ d obs, Å ( I, %) ( hkl )] are: 3.0762(100)(310), 2.8551(96)( $\bar 2$ 13), 2.9704(92)( $\bar 3$ 12), 2.8573(83)(013), 2.5552(66)(020), 2.8228(48)(212), 2.8893(40)(400), and 3.0634(30)(103).