Slawsonite Mineral Data

Slawsonite Mineral Data +

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General Slawsonite Information

Chemical Formula:

(Sr,Ca)Al2Si2O8

Composition:

Molecular Weight = 309.65 gm

Strontium 22.64 % Sr 26.77 % SrO

Calcium 1.29 % Ca 1.81 % CaO

Aluminum 15.68 % Al 29.64 % Al₂O₃

Silicon 19.05 % Si 40.75 % SiO₂

Oxygen 41.34 % O

______ ______

100.00 % 98.97 % = TOTAL OXIDE

Empirical Formula:

Sr_0.8Ca_0.1Al_1.8Si_2.1O₈

Environment:

In pectolite veinlets in metamorphosed xenoliths.

IMA Status:

Approved IMA 1977

Locality:

From the Wallowa Mountains, Wallowa County, Oregon, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Chester Baker Slawson (1898-1964, Mineralogist AT THE University of Michigan, Ann Arbor, Michigan, USA.

Synonym:

ICSD 100141

PDF 37-462

Slawsonite Image

Images:

Slawsonite

Comments: White crystalline slawsonite in rock.
Location: Sarisaka, Kagami, Kochi, Japan. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Slawsonite Crystallography

Axial Ratios:

a:b:c =0.9511:1:0.891

Cell Dimensions:

a = 8.888, b = 9.344, c = 8.326, Z = 4; beta = 90.33° V = 691.46 Den(Calc)= 2.97

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/a

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.708(1), 2.917(0.7), 3.498(0.64),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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Griffen D T , Ribbe P H , Gibbs G V , American Mineralogist , 62 (1977) p.31-35, The structure of slawsonite, a strontium analog of paracelsian

Physical Properties of Slawsonite

Cleavage:

[001] Good, [010] Fair

Color:

Colorless, Medium gray.

Density:

3.05 - 3.5, Average = 3.27

Diaphaniety:

Semitransparent

Habit:

Aggregates - Made of numerous individual crystals or clusters.

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

5.5-6.5 - Knife Blade-Pyrite

Luminescence:

Fluorescent, Short UV=pinkish red purple.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Slawsonite

Gladstone-Dale:

CI meas= 0.062 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= -0.034 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1951,KPDmeas= 0.1769,KC= 0.1887

Optical Data:

Biaxial (-), a=1.57-1.573, b=1.581-1.582, g=1.585-1.586, bire=0.0130-0.0150, 2V(Calc)=60-66, 2V(Meas)=55-82. Dispersion r < v medium.

Calculated Properties of Slawsonite

Electron Density:

r_electron=2.86 gm/cc
note: r_Slawsonite=2.97 gm/cc.

Fermion Index

Fermion Index = 0.02495
Boson Index = 0.97505

Photoelectric:

PE_Slawsonite= 26.20 barns/electron
U=PE_Slawsonite x r_electron= 74.99 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Slawsonite is Not Radioactive

Slawsonite Classification

Dana Class:

76.1.5.2 (76)Tectosilicate Al-Si Framework

(76.1)with Al-Si frameworks

(76.1.5)Paracelsian group

76.1.5.1 Paracelsian BaAl2Si2O8 P 2₁/c 2/m

76.1.5.2 Slawsonite (Sr,Ca)Al2Si2O8 P 2₁/a 2/m

Strunz Class:

VIII/J.06-80 VIII - Silicates

VIII/J - Tectosilicates (network) without anions unfamiliar to the tetraheders

VIII/J.06 - Feldspar group, Buddingtonite - Orthoclase - Slawsonite series

VIII/J.06-10 Buddingtonite (NH4)AlSi3O8·0.5(H2O) P 2₁ or P 2₁/m Mono

VIII/J.06-15 Kokchetavite! KAlSi3O8 P 6/mmm(?) 6/m 2/m 2/m

VIII/J.06-20 Sanidine (K,Na)(Si,Al)4O8 C 2/m 2/m

VIII/J.06-30 Microcline KAlSi3O8 C1 1

VIII/J.06-35 Rubicline! (Rb,K)AlSi3O8 P1 1

VIII/J.06-40 Orthoclase KAlSi3O8 C 2/m 2/m

VIII/J.06-50 Hyalophane (K,Ba)Al(Si,Al)3O8 C 2/m 2/m

VIII/J.06-60 Celsian BaAl2Si2O8 I21/c 2/m

VIII/J.06-70 Paracelsian BaAl2Si2O8 P 2₁/c 2/m

VIII/J.06-80 Slawsonite (Sr,Ca)Al2Si2O8 P 2₁/a 2/m

Other Slawsonite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(AntBidBlaNic2) OPTIC PROP.(AntBidBlaNic2)

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Slawsonite

(Sr,Ca)Al2Si2O8
Dana No: 76.1.5.2 Strunz No: VIII/J.06-80
Locality:

Notes: