Cookeite Mineral Data

Cookeite Mineral Data

General Cookeite Information

Chemical Formula:

LiAl4(Si3Al)O10(OH)8

Composition:

Molecular Weight = 522.16 gm

Lithium 1.33 % Li 2.86 % Li₂O

Aluminum 25.84 % Al 48.82 % Al₂O₃

Silicon 16.14 % Si 34.52 % SiO₂

Hydrogen 1.54 % H 13.80 % H₂O

Oxygen 55.15 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

LiAl₅Si₃O₁₀(OH)₈

Environment:

Alteration of lithia tourmalines and lepidolite in pegmatites.

IMA Status:

Valid Species (Pre-IMA) 1866

Locality:

Oxford Co., Maine, USA. Pala, San Diego Co., California, USA. Link to MinDat.org Location Data.

Cookeite Image

Images:

Cookeite

Comments: Large tan-colored cookeite epimorph after a large 12 cm quartz crystal. The outer faces of the epimorph are overgrown with milky quartz crystals up to 15 mm long.
Location: Bennett & Orchard Pit mines, Buckfield, Oxford Co., Maine, USA. Scale: 17x17x11 cm.
© John Betts - Fine Minerals

Cookeite Crystallography

Axial Ratios:

a:b:c =0.5744:1:3.2138

Cell Dimensions:

a = 5.13, b = 8.93, c = 28.7, Z = 4; beta = 98.75° V = 1,299.47 Den(Calc)= 2.67

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): 2.315(1), 3.52(0.9), 4.7(0.9),

Crystal Structure:

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Zheng H , Bailey S W , American Mineralogist , 82 (1997) p.1007-1013, Refinement of the cookeite r structure

Physical Properties of Cookeite

Cleavage:

[001] Perfect

Color:

White, Green, Brown, Yellowish white, Pinkish white.

Density:

2.67

Diaphaniety:

Transparent to translucent

Fracture:

Flexible - Flexible fragments.

Habit:

Micaceous - Platy texture with "flexible" plates.

Habit:

Pseudo Hexagonal - Crystals show a hexagonal outline.

Hardness:

2.5 - Finger Nail

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Cookeite

Gladstone-Dale:

CI meas= 0.044 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.044 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2185,KPDmeas= 0.2185,KC= 0.2286

Optical Data:

Biaxial (+), a=1.572-1.576, b=1.579-1.584, g=1.589-1.6, bire=0.0170-0.0240

Calculated Properties of Cookeite

Electron Density:

r_electron=2.68 gm/cc
note: r_Cookeite=2.67 gm/cc.

Fermion Index

Fermion Index = 0.00879
Boson Index = 0.99121

Photoelectric:

PE_Cookeite= 1.42 barns/electron
U=PE_Cookeite x r_electron= 3.79 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cookeite is Not Radioactive

Cookeite Classification

Dana Class:

71.4.1.2 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.4)interlayered 1:1, 2:1, and octahedra

(71.4.1)Chlorite group (Tri-Dioctahedral)

71.4.1.1 Donbassite Al2[Al2.33][Si3AlO10](OH)8 C 2/m 2/m

71.4.1.2 Cookeite LiAl4(Si3Al)O10(OH)8 P 2₁/a 2/m

71.4.1.3 Sudoite Mg2(Al,Fe)3Si3AlO10(OH)8 C 2/m 2/m

71.4.1.4 Clinochlore (Mg,Fe)5Al(Si3Al)O10(OH)8 C 2/m 2/m

71.4.1.5 Nimite (Ni,Mg,Fe)5Al(Si3Al)O10(OH)8 C 2/m 2/m

71.4.1.6 Baileychlore (Zn,Al,[])3[Fe2Al][Si3AlO10](OH)8 C1,C1 Tri

71.4.1.7 Chamosite (Fe,Mg,Fe)5Al(Si3Al)O10(OH,O)8 C 2/m 2/m

71.4.1.8 Pennantite Mn5Al(Si3Al)O10(OH)8 C 2/m 2/m

71.4.1.9 Orthochamosite! (Fe,Mg,Fe)5Al(Si3Al)O10(OH,O)8 C3m-pseudoHEX Ortho

71.4.1.10 Borocookeite! Li(13x)Al(4-x)(BSi3)O10(OH,F)8[x=0-0.33] pseudo C 2/m 2/m

Strunz Class:

VIII/H.23-90 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like with [Si4O10]4- and related groups

VIII/H.23 - Chlorite group

VIII/H.23-10 Sudoite Mg2(Al,Fe)3Si3AlO10(OH)8 C 2/m 2/m

VIII/H.23-20 Clinochlore (Mg,Fe)5Al(Si3Al)O10(OH)8 C 2/m 2/m

VIII/H.23-30 Chamosite (Fe,Mg,Fe)5Al(Si3Al)O10(OH,O)8 C 2/m 2/m

VIII/H.23-40 Orthochamosite (Fe,Mg,Fe)5Al(Si3Al)O10(OH,O)8 C3m-pseudoHEX Ortho

VIII/H.23-50 Baileychlore (Zn,Al,[])3[Fe2Al][Si3AlO10](OH)8 C1,C1 Tri

VIII/H.23-60 Pennantite Mn5Al(Si3Al)O10(OH)8 C 2/m 2/m

VIII/H.23-70 Nimite (Ni,Mg,Fe)5Al(Si3Al)O10(OH)8 C 2/m 2/m

VIII/H.23-80 Gonyerite Mn3[Mn3Fe][(Si,Fe)4O10](OH,O)8 pseudo-HEX Ortho

VIII/H.23-90 Cookeite LiAl4(Si3Al)O10(OH)8 P 2₁/a 2/m

VIII/H.23-95 Borocookeite! Li(13x)Al(4-x)(BSi3)O10(OH,F)8[x=0-0.33] pseudo C 2/m 2/m

VIII/H.23-100 Manandonite Li2Al4[(Si2AlB)O10](OH)8 C1 1

VIII/H.23-110 Franklinfurnaceite Ca2(Fe,Al)MnMn3Zn2Si2O10(OH)8 C 2 2

Other Cookeite Information

References:

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

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Cookeite

LiAl4(Si3Al)O10(OH)8
Dana No: 71.4.1.2 Strunz No: VIII/H.23-90
Locality:

Notes: