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Bobcookite

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Robert B. Cook
Formula:
NaAl(UO2)2(SO4)4·18H2O
Colour:
Lime green to greenish-yellow
Lustre:
Vitreous
Hardness:
Specific Gravity:
2.669 (Calculated)
Crystal System:
Triclinic
Name:
Named in honour of Dr. Robert B. “Bob” Cook (b. 1944), former distinguished professor and head of the Department of Geology and Geography at Auburn University, Auburn, Alabama.
Unique combination of elements. Stoichiometry and hydration level somewhat similar to that of the closely associated wetherillite.

In the structure there are (UO2)(SO4)2(H2O) chains (sheets of identical composition are found in wetherillite); the chains are connected by NaO4(H2O)2 octahedra thus forming layers; hydrogen bonds to insular Al(H2O)6 octahedra and isolated water groups stabilize the structure holding together the building elements. Composition of the coordination sphere in Na octahedra in wetherillite is different.


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Classification of BobcookiteHide

Approved
Approval Year:
2014
First Published:
2015

Pronounciation of BobcookiteHide

Pronounciation:
PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of BobcookiteHide

Vitreous
Transparency:
Transparent
Colour:
Lime green to greenish-yellow
Streak:
Very pale yellowish green
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Conchoidal
Density:
2.669 g/cm3 (Calculated)
Comment:
couldn't be measured

Optical Data of BobcookiteHide

Type:
Biaxial (-)
RI values:
nα = 1.501(1) nβ = 1.523(1) nγ = 1.536(1)
2V:
Measured: 78° to 74°
Max Birefringence:
δ = 0.035
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r < v, moderate
Pleochroism:
Visible
Comments:
X colourless, Y very pale yellow-green, Z pale yellow-green; X < Y < Z

Chemical Properties of BobcookiteHide

Formula:
NaAl(UO2)2(SO4)4·18H2O
IMA Formula:
NaAl(UO2)2(SO4)4 · 18H2O

Crystallography of BobcookiteHide

Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Setting:
P1
Cell Parameters:
a = 7.7912(2) Å, b = 10.5491(3) Å, c = 11.2451(8) Å
α = 68.961(5)°, β = 70.909(5)°, γ = 87.139(6)°
Ratio:
a:b:c = 0.739 : 1 : 1.066
Unit Cell V:
812.79 ų
Z:
1
Morphology:
Massive veins and columnar Crystals.
Twinning:
not observed

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
9.82(100)
7.14(99)
6.33(55)
5.99(39)
5.25(83)
3.563(52)
3.441(49)
3.082(57)
Comments:
From Type Description.

Type Occurrence of BobcookiteHide

General Appearance of Type Material:
irregular, columnar, crude prisms, up to 2 mm, often curved; may be composite; [10_1] elongation, irregular terminations; forms observed: {010}, {101}, {111}, {1_11}
Place of Conservation of Type Material:
Type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA, catalogue number 64164, and the Fersman Mineralogical Museum of the Russian Academy of S
Geological Setting of Type Material:
secondary alteration phase in efflorescences on mine walls
Associated Minerals at Type Locality:

Synonyms of BobcookiteHide

Other Language Names for BobcookiteHide

Fluorescence of BobcookiteHide

Bright greenish-white

Other InformationHide

Notes:
Moderately hygroscopic; easily soluble in cold (RT) water; Raman bands [cm-1]: ~3600–3000 [υ(O-H) stretching of free or weakly H-bonded water], 1640 [υ2(δ) H-O-H bending], 1210, 1145, 1110 [split triply degenerate υ3 sulfate antisymmetric stretching], 1035(s,b) 1010(s,b) [υ1 sulfate symmetric stretching], 990sh [δ(U-OH) bending or υ1 of sulfate], 845vs [υ1 symmetric stretching of uranyl groups], 630. 600 [split, triply degenerate υ4(δ) of sulfate], 470, 450 [split doubly degenerate υ2(δ) sulfate bending], 330 [υ(U-Oequatorial) or Na-O stretching], 210 [composite band, split doubly degenerate υ2(δ) uranyl bending]
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 BobcookiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Kampf, A.R., Pla´sˇil, J., Kasatkin, A.V. and Marty, J. (2014) Bobcookite, IMA 2014-030. CNMNC Newsletter No. 21, August 2014, page 802. Mineralogical Magazine: 78: 797-804.
Kampf, A.R., Plášil, J., Kasatkin, A.V., Marty, J. (2015) Bobcookite, NaAl(UO2)2(SO4)4·18H2O and wetherillite, Na2Mg(UO2)2(SO4)4·18H2O, two new uranyl sulfate minerals from the Blue Lizard mine, San Juan County, Utah, USA. Mineralogical Magazine: 79: 695-714; in: Gagne, O.C., Belakovskiy, D.I., Cámara, F. (2016): New mineral names. American Mineralogist: 101: 1240-1243

Internet Links for BobcookiteHide

Localities for BobcookiteHide

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.
USA (TL)
 
  • Utah
    • San Juan Co.
      • White Canyon District
        • Red Canyon
Kampf, A.R., Pla´sˇil, J., Kasatkin, A.V. and Marty, J. (2014) Bobcookite, IMA 2014-030. CNMNC Newsletter No. 21, August 2014, page 802; Mineralogical Magazine, 78, 797-804. ; Kampf, A.R., Plášil, J., Kasatkin, A.V., Marty, J. (2015): Bobcookite, NaAl(UO2)2(SO4)4·18H2O and wetherillite, Na2Mg(UO2)2(SO4)4·18H2O, two new uranyl sulfate minerals from the Blue Lizard mine, San Juan County, Utah, USA. Mineralogical Magazine, 79, 695-714.
Travis Olds collection
Mineral and/or Locality  
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