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Barrydawsonite-(Y)

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Formula:
Na1.5Y0.5CaSi3O9H
Colour:
Colourless
Crystal System:
Monoclinic
Name:
Name is for Professor John Barry Dawson (19 June 1932 - 2 February 2013, Edinburgh, Scotland), an eminent British petrologist who made ground-breaking studies of silica undersaturated rocks of the Earth’s crust and mantle. He was particularly well-known for his discovery of the world’s only active carbonatite volcano, Oldoinyo Lengai (Tanzania). Over his career he worked at the Tanganyika Geological Survey, and the universities of St Andrews, Sheffield, and Edinburgh. Prof. Dawson also had a long association with the International Kimberlite Conferences, of which he was a co-founder.
A pyroxenoid closely related to the Pectolite-Sérandite Series. Barrydawsonite-(Y) is related to pectolite by the substitution ½[NaM3+Ca−2] (M3+ = Y,REE), and the only member of the wollastonite group that has the structure of the monoclinic M2abc polytype. Chemically the mineral is somewhat similar to gerenite-(Y), monteregianite-(Y), and yakovenchukite-(Y).
Barrydawsonite-(Y) crystals from the TL commonly have discrete thin rims of Y-bearing pectolite.

The structure contains three metal sites: M(1) is Ca, M(2) is Na0.5(Y,REE)0.5, and M(3) is Na. Coordination number of the sites is the same as in pectolite and serandite, and equals 6 for M(1) and M(2), or 8 for M(3). The M(2)-centred octahedron participates in hydrogen bonding.


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Classification of Barrydawsonite-(Y)Hide

Approved
Approval Year:
2014
First Published:
2015

Physical Properties of Barrydawsonite-(Y)Hide

Colour:
Colourless

Optical Data of Barrydawsonite-(Y)Hide

Type:
Biaxial (+)
RI values:
nα = 1.612(1) nβ = 1.617(1) nγ = 1.630(1)
2V:
Measured: 63°
Max Birefringence:
δ = 0.018
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
moderate dispersion r < v.
Pleochroism:
Non-pleochroic

Chemical Properties of Barrydawsonite-(Y)Hide

Formula:
Na1.5Y0.5CaSi3O9H
IMA Formula:
Na1.5Y0.5CaSi3O9H
Idealised Formula:
Na(Na0.5Y0.5)Ca[Si3O8(OH)]
Common Impurities:
Mn,(Fe,Dy)

Crystallography of Barrydawsonite-(Y)Hide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/a
Cell Parameters:
a = 15.5026(2) Å, b = 7.0233(1) Å, c = 6.9769(1) Å
γ = 95.149(1)°
Ratio:
a:b:c = 2.207 : 1 : 0.993
Unit Cell V:
756.58 ų
Z:
4
Morphology:
brown crystals (<1 vol.%) included in amphibole and/or pyroxene

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
3.272(27)
3.094(30)
2.905(100)
2.721(17)
2.421(16)
2.161(27)
1.7613(29)
1.7016(27)
Comments:
From Type Description.

Type Occurrence of Barrydawsonite-(Y)Hide

General Appearance of Type Material:
forms single grains which can be either subhedral prismatic crystals up to 0.2mm x
0.1mm x 0.1mm, or anhedral crystals up to
0.5mm in maximum dimension.
Place of Conservation of Type Material:
Type material is deposited in the collections of the Natural History Museum, London, UK, catalogue number BM 2014-50. Cotype material is deposited in the collections of the Natural History Museum of Los Angeles County, California, USA, catalogue number 64
Geological Setting of Type Material:
Metamorphosed eudialyte syenite
Associated Minerals at Type Locality:
Reference:
Mitchell, R.H., Welch, M.D., Kampf, A.R., Chakhmouradian, A.K., Spratt, J. (2015) Barrydawsonite-(Y), Na1.5CaY0.5Si3O9H: a new pyroxenoid of the pectolite–serandite group. Mineralogical Magazine: 79: 671-686.

Synonyms of Barrydawsonite-(Y)Hide

Relationship of Barrydawsonite-(Y) to other SpeciesHide

Other Members of this group:
BustamiteCaMn2+(Si2O6)Tric. 1 : P1
CascanditeCa(Sc,Fe3+)(HSi3O9)Tric. 1
FerrobustamiteCaFe2+(Si2O6)Tric.
MurakamiiteCa2LiSi3O8(OH)Tric. 1 : P1
PectoliteNaCa2Si3O8(OH)Tric. 1 : P1
SchizoliteNaCaMnSi3O8(OH)Tric. 1 : P1
SeranditeNaMn2+2Si3O8(OH)Tric. 1 : P1
TanohataiteLiMn2(HSi3O9)Tric. 1 : P1
VistepiteSnMn4B2Si4O16(OH)2Tric. 1
WollastoniteCaSiO3Tric. 1 : P1

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Barrydawsonite-(Y)Hide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Mitchell, R.H., Welch, M.D., Kampf, A.R., Chakhmouradian, A. and Spratt, J. (2014) Barrydawsonite-(Y), IMA 2014-042. CNMNC Newsletter No. 22, October 2014, page 1242. Mineralogical Magazine: 78: 1241-1248.
Mitchell, R.H., Welch, M.D., Kampf, A.R., Chakhmouradian, A.K., Spratt, J. (2015) Barrydawsonite-(Y), Na1.5CaY0.5Si3O9H: a new pyroxenoid of the pectolite–serandite group. Mineralogical Magazine: 79: 671-686.

Internet Links for Barrydawsonite-(Y)Hide

Localities for Barrydawsonite-(Y)Hide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Canada (TL)
 
  • Newfoundland and Labrador
    • Labrador
      • North Red Wine Pluton
Mitchell, R.H., Welch, M.D., Kampf, A.R., Chakhmouradian, A. and Spratt, J. (2014) Barrydawsonite-(Y), IMA 2014-042. CNMNC Newsletter No. 22, October 2014, page 1242; Mineralogical Magazine, 78, 1241-1248; Mitchell, R.H., Welch, M.D., Kampf, A.R., Chakhmouradian, A.K., Spratt, J. (2015): Barrydawsonite-(Y), Na1.5CaY0.5Si3O9H: a new pyroxenoid of the pectolite–serandite group. Mineralogical Magazine, 79, 671-686.
Mineral and/or Locality  
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