Dawsonite Mineral Data

Dawsonite Mineral Data +

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General Dawsonite Information

Chemical Formula:

NaAl(CO3)(OH)2

Composition:

Molecular Weight = 144.00 gm

Sodium 15.97 % Na 21.52 % Na₂O

Aluminum 18.74 % Al 35.40 % Al₂O₃

Hydrogen 1.40 % H 12.51 % H₂O

Carbon 8.34 % C 30.56 % CO₂

Oxygen 55.56 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

NaAl(CO₃)(OH)₂

IMA Status:

Valid Species (Pre-IMA) 1874

Locality:

Feldspathic dike near McGill university, Montreal, Canada. Link to MinDat.org Location Data.

Name Origin:

Named after the Canadian geologist, J. W. Dawson (1820-1899).

Synonym:

ICSD 100140

PDF 42-1346

Dawsonite Image

Images:

Dawsonite

Comments: White, radial crystalline aggregates of dawsonite crystals.
Location: Mont St. Hilaire, Quebec, Canada. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Dawsonite Crystallography

Axial Ratios:

a:b:c =0.6496:1:0.5381

Cell Dimensions:

a = 6.73, b = 10.36, c = 5.575, Z = 4; V = 388.70 Den(Calc)= 2.46

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: Imam

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

By Intensity(I/I_o): 5.7(1), 3.385(0.16), 1.69(0.14),

Forms:

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Forms: [ 0 1 0] [ 0 1 1] [ 1 1 0] [ 1 0 0] [ 0 0 1]

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Crystal Structure:

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Frueh A J , Golightly J P , The Canadian Mineralogist , 9 (1967) p.51-56, The crystal structure of dawsonite NaAl(CO3)(OH)2, Locality: McGill University, Montreal, Quebec, Canada

Physical Properties of Dawsonite

Cleavage:

[110] Perfect

Color:

Colorless, White.

Density:

2.4 - 2.44, Average = 2.42

Diaphaniety:

Transparent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Acicular - Occurs as needle-like crystals.

Habit:

Encrustations - Forms crust-like aggregates on matrix.

Habit:

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

Hardness:

3 - Calcite

Luminescence:

Fluorescent, Short UV=dull white.

Luster:

Vitreous - Silky

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Dawsonite

Gladstone-Dale:

CI meas= 0.001 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.017 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2173,KPDmeas= 0.2209,KC= 0.2212

Optical Data:

Biaxial (-), a=1.466, b=1.542, g=1.596, bire=0.1300, 2V(Calc)=76, 2V(Meas)=77. Dispersion relatively weak.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Dawsonite

Electron Density:

r_electron=2.42 gm/cc
note: r_Dawsonite=2.42 gm/cc.

Fermion Index

Fermion Index = 0.00118
Boson Index = 0.99882

Photoelectric:

PE_Dawsonite= 0.94 barns/electron
U=PE_Dawsonite x r_electron= 2.27 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Dawsonite is Not Radioactive

Dawsonite Classification

Dana Class:

16a.3.8.1 (16a)Carbonates - Hydroxyl or Halogen

(16a.3)where (A B)2 (XO3) Zq

(16a.3.8)Dana Group

16a.3.8.1 Dawsonite NaAl(CO3)(OH)2 Imam 2/m 2/m 2/m

Strunz Class:

V/C.02-20 V - Nitrates, Carbonates and Borates

V/C - Waterfree carbonates with unfamiliar anions

V/C.02 - Barentsite - Tunisite series

V/C.02-10 Barentsite Na7AlH2(CO3)4F4 P1 or P1 Tri

V/C.02-20 Dawsonite NaAl(CO3)(OH)2 Imam 2/m 2/m 2/m

V/C.02-30 Tunisite NaCa2Al4(CO3)4(OH)8Cl P 4/nmm 4/m 2/m 2/m

Other Dawsonite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Print or Cut-and-Paste your Dawsonite Specimen Label here :

Dawsonite

NaAl(CO3)(OH)2
Dana No: 16a.3.8.1 Strunz No: V/C.02-20
Locality:

Notes: