Sazhinite-(La), Na3LaSi6O15 (H2O)2, a new mineral from the Aris phonolite, Namibia: Description and crystal structure

F. Cámara, L. Ottolini, B. Devouard, Laurence Garvie, F. C. Hawthorne

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Sazhinite-(La) is a new mineral from the Axis phonolite, Windhoek, Namibia. It occurs in vesicles within the phonolite, together with other species crystallized from late-stage hydrothermal fluids: natrolite, aegirine, microcline, apophyllite, sphalerite, analcime, fluorite, villiaumite hydroxylapatite, galena, makatite, quartz, eudialyte, kanemite, tuperssuatsiaite and korobitsynite. Sazhinite-(La) forms small euhedral crystals up to 1 mm long and 0.4 mm wide, elongated along [001] and flattened on (010), exhibiting the forms {h01}, {100} and {001}. It has good cleavage parallel to {010} and {001}. Twinning was not observed. Crystals are brittle with a Mohs hardness of 3, creamy white with a white streak, vitreous to pearly lustre, and translucent to transparent. In plane-polarized light, crystals are colourless with a = Z, b = Y, c = X. It is biaxial positive with α = 1.524, β = 1.528, γ = 1.544, all ±0.002, 2VZ(obs) = 46(1)°, and 2VZ(calc.) = 53.6°. Sazhinite-(La) is orthorhombic Pmm2, a = 7.415(2), b = 15.515(3), c = 7.164(1) Å, and V = 824.2 Å3. One crystal was studied by X-ray diffraction, electron microprobe and secondary ion mass spectrometry (SIMS) microanalysis, leading to the average composition (Na2.87K0.02Sr0.001)∑2.90 [La0.41Ce0.35Pr0.02Nd0.04 (Sm,Gd,Dy,Er,Yb)∑0.01,Th0.09U0.01 Y0.01Zr0.01Ca0.08Li0.01] ∑1.044T(Si5.87Si0.06 B0.01) (O14.86F0.14)· (H2O)2. Weighted full-matrix least-squares refinement on 3369 reflections yielded Rall = 3.8%. The structure is built of corrugated [Si6O15]6- layers linked by [7]-coordinated REE and R4+ cations. This framework leaves channels that contain three [5]- and [6]-coordinated Na cations per formula unit that compensate for the residual charge on the silicate layers. The SIMS analyses confirm a Na content of 3 atoms per formula unit, leading to an ideal formula of Na3LaSi6O15(H2O)2. The third Na atom is bonded to H2O groups and therefore the total content of both Na and H2O may be reduced to 2 and 1 per formula, respectively. The depletion in Na allows for the entrance of high-charge cations such as Th4+.

Original languageEnglish (US)
Pages (from-to)405-418
Number of pages14
JournalMineralogical Magazine
Volume70
Issue number4
DOIs
StatePublished - Aug 1 2006

Fingerprint

phonolite
new mineral
crystal structure
Minerals
Crystal structure
crystal
Cations
Crystals
cation
Secondary ion mass spectrometry
mass spectrometry
eudialyte
natrolite
analcime
Silicates
aegirine
Atoms
Quartz
microcline
twinning

Keywords

  • EMPA
  • New mineral
  • Rare-earth minerals
  • Sazhinite-(La)
  • SCXRD
  • SIMS

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Sazhinite-(La), Na3LaSi6O15 (H2O)2, a new mineral from the Aris phonolite, Namibia : Description and crystal structure. / Cámara, F.; Ottolini, L.; Devouard, B.; Garvie, Laurence; Hawthorne, F. C.

In: Mineralogical Magazine, Vol. 70, No. 4, 01.08.2006, p. 405-418.

Research output: Contribution to journalArticle

Cámara, F. ; Ottolini, L. ; Devouard, B. ; Garvie, Laurence ; Hawthorne, F. C. / Sazhinite-(La), Na3LaSi6O15 (H2O)2, a new mineral from the Aris phonolite, Namibia : Description and crystal structure. In: Mineralogical Magazine. 2006 ; Vol. 70, No. 4. pp. 405-418.
@article{b175ecc9555e4fc3a62ebb147ae3e3ab,
title = "Sazhinite-(La), Na3LaSi6O15 (H2O)2, a new mineral from the Aris phonolite, Namibia: Description and crystal structure",
abstract = "Sazhinite-(La) is a new mineral from the Axis phonolite, Windhoek, Namibia. It occurs in vesicles within the phonolite, together with other species crystallized from late-stage hydrothermal fluids: natrolite, aegirine, microcline, apophyllite, sphalerite, analcime, fluorite, villiaumite hydroxylapatite, galena, makatite, quartz, eudialyte, kanemite, tuperssuatsiaite and korobitsynite. Sazhinite-(La) forms small euhedral crystals up to 1 mm long and 0.4 mm wide, elongated along [001] and flattened on (010), exhibiting the forms {h01}, {100} and {001}. It has good cleavage parallel to {010} and {001}. Twinning was not observed. Crystals are brittle with a Mohs hardness of 3, creamy white with a white streak, vitreous to pearly lustre, and translucent to transparent. In plane-polarized light, crystals are colourless with a = Z, b = Y, c = X. It is biaxial positive with α = 1.524, β = 1.528, γ = 1.544, all ±0.002, 2VZ(obs) = 46(1)°, and 2VZ(calc.) = 53.6°. Sazhinite-(La) is orthorhombic Pmm2, a = 7.415(2), b = 15.515(3), c = 7.164(1) {\AA}, and V = 824.2 {\AA}3. One crystal was studied by X-ray diffraction, electron microprobe and secondary ion mass spectrometry (SIMS) microanalysis, leading to the average composition (Na2.87K0.02Sr0.001)∑2.90 [La0.41Ce0.35Pr0.02Nd0.04 (Sm,Gd,Dy,Er,Yb)∑0.01,Th0.09U0.01 Y0.01Zr0.01Ca0.08Li0.01] ∑1.044T(Si5.87Si0.06 B0.01) (O14.86F0.14)· (H2O)2. Weighted full-matrix least-squares refinement on 3369 reflections yielded Rall = 3.8{\%}. The structure is built of corrugated [Si6O15]6- layers linked by [7]-coordinated REE and R4+ cations. This framework leaves channels that contain three [5]- and [6]-coordinated Na cations per formula unit that compensate for the residual charge on the silicate layers. The SIMS analyses confirm a Na content of 3 atoms per formula unit, leading to an ideal formula of Na3LaSi6O15(H2O)2. The third Na atom is bonded to H2O groups and therefore the total content of both Na and H2O may be reduced to 2 and 1 per formula, respectively. The depletion in Na allows for the entrance of high-charge cations such as Th4+.",
keywords = "EMPA, New mineral, Rare-earth minerals, Sazhinite-(La), SCXRD, SIMS",
author = "F. C{\'a}mara and L. Ottolini and B. Devouard and Laurence Garvie and Hawthorne, {F. C.}",
year = "2006",
month = "8",
day = "1",
doi = "10.1180/0026461067040343",
language = "English (US)",
volume = "70",
pages = "405--418",
journal = "Mineralogical Magazine",
issn = "0026-461X",
publisher = "Mineralogical Society",
number = "4",

}

TY - JOUR

T1 - Sazhinite-(La), Na3LaSi6O15 (H2O)2, a new mineral from the Aris phonolite, Namibia

T2 - Description and crystal structure

AU - Cámara, F.

AU - Ottolini, L.

AU - Devouard, B.

AU - Garvie, Laurence

AU - Hawthorne, F. C.

PY - 2006/8/1

Y1 - 2006/8/1

N2 - Sazhinite-(La) is a new mineral from the Axis phonolite, Windhoek, Namibia. It occurs in vesicles within the phonolite, together with other species crystallized from late-stage hydrothermal fluids: natrolite, aegirine, microcline, apophyllite, sphalerite, analcime, fluorite, villiaumite hydroxylapatite, galena, makatite, quartz, eudialyte, kanemite, tuperssuatsiaite and korobitsynite. Sazhinite-(La) forms small euhedral crystals up to 1 mm long and 0.4 mm wide, elongated along [001] and flattened on (010), exhibiting the forms {h01}, {100} and {001}. It has good cleavage parallel to {010} and {001}. Twinning was not observed. Crystals are brittle with a Mohs hardness of 3, creamy white with a white streak, vitreous to pearly lustre, and translucent to transparent. In plane-polarized light, crystals are colourless with a = Z, b = Y, c = X. It is biaxial positive with α = 1.524, β = 1.528, γ = 1.544, all ±0.002, 2VZ(obs) = 46(1)°, and 2VZ(calc.) = 53.6°. Sazhinite-(La) is orthorhombic Pmm2, a = 7.415(2), b = 15.515(3), c = 7.164(1) Å, and V = 824.2 Å3. One crystal was studied by X-ray diffraction, electron microprobe and secondary ion mass spectrometry (SIMS) microanalysis, leading to the average composition (Na2.87K0.02Sr0.001)∑2.90 [La0.41Ce0.35Pr0.02Nd0.04 (Sm,Gd,Dy,Er,Yb)∑0.01,Th0.09U0.01 Y0.01Zr0.01Ca0.08Li0.01] ∑1.044T(Si5.87Si0.06 B0.01) (O14.86F0.14)· (H2O)2. Weighted full-matrix least-squares refinement on 3369 reflections yielded Rall = 3.8%. The structure is built of corrugated [Si6O15]6- layers linked by [7]-coordinated REE and R4+ cations. This framework leaves channels that contain three [5]- and [6]-coordinated Na cations per formula unit that compensate for the residual charge on the silicate layers. The SIMS analyses confirm a Na content of 3 atoms per formula unit, leading to an ideal formula of Na3LaSi6O15(H2O)2. The third Na atom is bonded to H2O groups and therefore the total content of both Na and H2O may be reduced to 2 and 1 per formula, respectively. The depletion in Na allows for the entrance of high-charge cations such as Th4+.

AB - Sazhinite-(La) is a new mineral from the Axis phonolite, Windhoek, Namibia. It occurs in vesicles within the phonolite, together with other species crystallized from late-stage hydrothermal fluids: natrolite, aegirine, microcline, apophyllite, sphalerite, analcime, fluorite, villiaumite hydroxylapatite, galena, makatite, quartz, eudialyte, kanemite, tuperssuatsiaite and korobitsynite. Sazhinite-(La) forms small euhedral crystals up to 1 mm long and 0.4 mm wide, elongated along [001] and flattened on (010), exhibiting the forms {h01}, {100} and {001}. It has good cleavage parallel to {010} and {001}. Twinning was not observed. Crystals are brittle with a Mohs hardness of 3, creamy white with a white streak, vitreous to pearly lustre, and translucent to transparent. In plane-polarized light, crystals are colourless with a = Z, b = Y, c = X. It is biaxial positive with α = 1.524, β = 1.528, γ = 1.544, all ±0.002, 2VZ(obs) = 46(1)°, and 2VZ(calc.) = 53.6°. Sazhinite-(La) is orthorhombic Pmm2, a = 7.415(2), b = 15.515(3), c = 7.164(1) Å, and V = 824.2 Å3. One crystal was studied by X-ray diffraction, electron microprobe and secondary ion mass spectrometry (SIMS) microanalysis, leading to the average composition (Na2.87K0.02Sr0.001)∑2.90 [La0.41Ce0.35Pr0.02Nd0.04 (Sm,Gd,Dy,Er,Yb)∑0.01,Th0.09U0.01 Y0.01Zr0.01Ca0.08Li0.01] ∑1.044T(Si5.87Si0.06 B0.01) (O14.86F0.14)· (H2O)2. Weighted full-matrix least-squares refinement on 3369 reflections yielded Rall = 3.8%. The structure is built of corrugated [Si6O15]6- layers linked by [7]-coordinated REE and R4+ cations. This framework leaves channels that contain three [5]- and [6]-coordinated Na cations per formula unit that compensate for the residual charge on the silicate layers. The SIMS analyses confirm a Na content of 3 atoms per formula unit, leading to an ideal formula of Na3LaSi6O15(H2O)2. The third Na atom is bonded to H2O groups and therefore the total content of both Na and H2O may be reduced to 2 and 1 per formula, respectively. The depletion in Na allows for the entrance of high-charge cations such as Th4+.

KW - EMPA

KW - New mineral

KW - Rare-earth minerals

KW - Sazhinite-(La)

KW - SCXRD

KW - SIMS

UR - http://www.scopus.com/inward/record.url?scp=33751222255&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33751222255&partnerID=8YFLogxK

U2 - 10.1180/0026461067040343

DO - 10.1180/0026461067040343

M3 - Article

AN - SCOPUS:33751222255

VL - 70

SP - 405

EP - 418

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 4

ER -