Lawsonite Mineral Data

Lawsonite Mineral Data +

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General Lawsonite Information

Chemical Formula:

CaAl2Si2O7(OH)2·(H2O)

Composition:

Molecular Weight = 314.24 gm

Calcium 12.75 % Ca 17.85 % CaO

Aluminum 17.17 % Al 32.45 % Al₂O₃

Silicon 17.88 % Si 38.24 % SiO₂

Hydrogen 1.28 % H 11.47 % H₂O

Oxygen 50.91 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

CaAl₂Si₂O₇(OH)₂·(H₂O)

Environment:

Originally described from a crystalline schist associated with serpentine. Also found as a secondary mineral in altered gabbros and diorites.

IMA Status:

Valid Species (Pre-IMA) 1895

Locality:

Reed Station, Tiburon peninsula, Marin County, California, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Andrew Cowper Lawson (1861-1952), Scottish-American geologist.

Synonym:

ICSD 80835

PDF 13-533

Lawsonite Image

Images:

Lawsonite

Comments: Glaucophane schist with a heavy druse of lawsonite crystals.
Location: Reed Station, Tiburon, Marin County, California, USA. Scale: Crystal size 7 mm.
© John Veevaert

Lawsonite Crystallography

Axial Ratios:

a:b:c =1.5051:1:2.2488

Cell Dimensions:

a = 8.79, b = 5.84, c = 13.133, Z = 4; V = 674.16 Den(Calc)= 3.10

Crystal System:

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

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

By Intensity(I/I_o): 2.624(1), 1.55(0.8), 2.726(0.7),

Crystal Structure:

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Baur W H , American Mineralogist , 63 (1978) p.311-315, Crystal structure refinement of lawsonite, Locality: Tiburon Peninsula, Marin County, California, USA

View Additional jPOWD Structure files for Lawsonite
[1] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [2] [20] [21] [22] [23] [24] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Lawsonite

Cleavage:

[010] Perfect, [001] Perfect, [110] Poor

Color:

Colorless, White, Gray, Blue, Pinkish.

Density:

3.09

Diaphaniety:

Translucent to transparent

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

7.5 - Garnet

Luminescence:

None.

Luster:

Vitreous - Greasy

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Lawsonite

Gladstone-Dale:

CI meas= 0.022 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.025 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2176,KPDmeas= 0.2183,KC= 0.2232

Optical Data:

Biaxial (+), a=1.665, b=1.672-1.676, g=1.684-1.686, bire=0.0190-0.0210, 2V(Calc)=76-86, 2V(Meas)=84-85. Dispersion strong, r > v.

Pleochroism (x):

colorless or blue.

Pleochroism (y):

colorless or yellow.

Pleochroism (z):

colorless or colorless.

Calculated Properties of Lawsonite

Electron Density:

r_electron=3.11 gm/cc
note: r_Lawsonite=3.09 gm/cc.

Fermion Index

Fermion Index = 0.00876
Boson Index = 0.99124

Photoelectric:

PE_Lawsonite= 2.77 barns/electron
U=PE_Lawsonite x r_electron= 8.60 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Lawsonite is Not Radioactive

Lawsonite Classification

Dana Class:

56.2.3.1 (56)Sorosilicate Si2O7 Groups and O, OH, F. and H2O

(56.2)with cations in [4] and/or >[4] coordination

(56.2.3)Lawsonite - Ilvaite group

56.2.3.1 Lawsonite CaAl2Si2O7(OH)2·(H2O) Ccmm 2/m 2/m 2/m

56.2.3.2 Hennomartinite SrMn2Si2O7(OH)2·(H2O) C mcm 2/m 2/m 2/m

56.2.3.3 Ilvaite CaFe2FeSi2O7O(OH) Pbnm 2/m 2/m 2/m

56.2.3.4 Noelbensonite! BaMn2(Si2O7)(OH)2·(H2O) C mcm 2/m 2/m 2/m

56.2.3.5 Itoigawaite! SrAl2Si2O7(OH)2·(H2O) C mcm 2/m 2/m 2/m

56.2.3.6 IMA2002-016! CaFeFe(Mn,Fe)(Si2O7)O(OH) P 2₁/a 2/m

Strunz Class:

VIII/C.10-10 VIII - Silicates

VIII/C - Sorosilicates with [Si2O7]6-, with anions unfamiliar to tetraheders [O,OH,F]

VIII/C.10 - Lawsonite - Ilvaite series

VIII/C.10-10 Lawsonite CaAl2Si2O7(OH)2·(H2O) Ccmm 2/m 2/m 2/m

VIII/C.10-12 Itoigawaite! SrAl2Si2O7(OH)2·(H2O) C mcm 2/m 2/m 2/m

VIII/C.10-15 Hennomartinite SrMn2Si2O7(OH)2·(H2O) C mcm 2/m 2/m 2/m

VIII/C.10-17 Noelbensonite! BaMn2(Si2O7)(OH)2·(H2O) C mcm 2/m 2/m 2/m

VIII/C.10-20 Ilvaite CaFe2FeSi2O7O(OH) Pbnm 2/m 2/m 2/m

Other Lawsonite Information

References:

NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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

Lawsonite

CaAl2Si2O7(OH)2·(H2O)
Dana No: 56.2.3.1 Strunz No: VIII/C.10-10
Locality:

Notes: