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Glauconite

Big Photo

Bertocchi quarry (ex Alvese quarry), San Pietro Mussolino, Vicenza Province, Veneto, Italy
© Chinellato Matteo

Show Glauconite Photos (8)
Formula:
K
 
0.08
R
1
1.33
 R
2
0.67
 [][Al
 
0.13
Si
 
3.87
O
 
10
](OH)
 
2
System:MonoclinicColour:Blue-green, ...
Hardness:2
Name:Named in 1828 from the Greek "glaukos," blue-green, in allusion to its color; but the term "glauconie" was used earlier, in 1823.


Typically found as rounded aggregates or "pellets" of very fine grained scaly particles, having a blue-green to yellow-green color.

Classification of Glauconite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Explanation of status:The name is for a series in the Mica Group, not an individual species. While it is currently accepted, it is likely that once the species in the series have been better defined it will be replaced by two or more species names.
Strunz 8th edition ID:8/H.13-40

8 : Silicates
H : Phyllosilicates (layered), Tetragonal or pseudotetragonal layered structures [Si4O10]4- and others
13 : Mica group - Glauconite series
Dana 7th edition ID:71.2.2.5
Dana 8th edition ID:71.2.2a.5

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
Hey's CIM Ref.:16.20.10

16 : Silicates Containing Aluminum and other Metals
20 : Aluminosilicates of Fe, Mg and alkalis
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Occurrences of Glauconite

Geological Setting:Formed in shallow marine environments that are mildly reducing when little or no sedimentation is taking place, hence found in shallow marine sedimentary rocks - limestones, siltstones, shales and sandstones. "Greenstones" are named that because if their typically high glauconite content.

Physical Properties of Glauconite

Lustre:Dull, Earthy
Diaphaneity (Transparency):Translucent, Opaque
Colour:Blue-green, yellow-green, green, rarely colorless.
Streak:None
Hardness (Mohs):2
Hardness Data:Measured
Tenacity:Elastic
Cleavage:Perfect
Perfect on {001}.
Fracture:Micaeous
Density (measured):2.4 - 2.95 g/cm3
Density (calculated):2.9 g/cm3

Crystallography of Glauconite

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:B2/m (B1 1 2/m) [C2/m] {C1 2/m 1}
Cell Parameters:a = 5.234Å, b = 9.066Å, c = 10.16Å
β = 100.5°
Ratio:a:b:c = 0.577 : 1 : 1.121
Unit Cell Volume:V 474.03 ų (Calculated from Unit Cell)
Z:2
Morphology:Crystals extremely rare; typically found as rounded aggregates of very fine grained scaly particles, more rarely as tiny laths or platelets.
X-Ray Powder Diffraction:
d-spacingIntensity
10.1(100)
4.53(80)
3.63(400
3.33(60)
3.09(40)
2.59(100)
2.40(60)
Comments:The -1M and -3T polytypes cannot be distinguised by the powder pattern.

Optical Data of Glauconite

Type:Biaxial (-)
RI values: nα = 1.590 - 1.612 nβ = 1.609 - 1.643 nγ = 1.610 - 1.644
2V:Calculated: 20° to 24°
Maximum Birefringence:δ = 0.020 - 0.032

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate
Dispersion:r > v

Chemical Properties of Glauconite

Formula:
K
 
0.08
R
1
1.33
 R
2
0.67
 [][Al
 
0.13
Si
 
3.87
O
 
10
](OH)
 
2
Essential elements:Fe, H, K, O, Si
All elements listed in formula:Al, H, K, O, Si
Common Impurities:Ti,Ca,P

Relationship of Glauconite to other Species

Related to:
  • Mica Group
    • Related Minerals - Strunz Grouping):

    - +
    8/H.13-10Wonesite
    (Na,K)(Mg,fe,Al)
     
    6
    		(Al,Si)
     
    8
    		O
     
    20
    		(OH,F)
     
    4
    8/H.13-20Brammallite
    Na
     
    0.65
    		Al
     
    2.0
    		ٱAl
     
    0.65
    		Si
     
    3.35
    		O
     
    10
    		(OH)
     
    2
    Related Minerals - Hey's Index Grouping:

    - +
    16.20.1Glaucophane
    [ ][Na
     
    2
    		][Mg
     
    3
    		Al
     
    2
    		][(OH)
     
    2
    		|Si
     
    8
    		O
     
    22
    		]
    16.20.2Sodium-anthophyllite
    16.20.3Sodium Gedrite
    16.20.4Crossite
    16.20.5Ferro-eckermannite
    [Na][Na
     
    2
    		][(Fe
    2+
     
    		,Mg)
     
    4
    		Al][(OH)
     
    2
    		|Si
     
    8
    		O
     
    22
    		]
    16.20.6Wonesite
    (Na,K)(Mg,fe,Al)
     
    6
    		(Al,Si)
     
    8
    		O
     
    20
    		(OH,F)
     
    4
    16.20.8Lennilenapeite
    K
     
    6-7
    		(Mg,Mn,Fe,Zn)
     
    48
    		(Si,Al)
     
    72
    		(O,OH)
     
    216
    		·16H
     
    2
    		O
    16.20.9Stilpnomelane
    K(Fe
    2+
     
    		,Mg,Fe
    3+
     
    		)
     
    8
    		(Si,Al)
     
    12
    		(O,OH)
     
    27
    Related Minerals - Dana Grouping):

    - +
    71.2.2.1Muscovite
    KAl
     
    2
    		[(OH)
     
    2
    		|AlSi
     
    3
    		O
     
    10
    		]
    71.2.2.2Illite
    K
     
    0.65
    		A
     
    2.0
    		 [][Al
     
    0.65
    		Si,
     
    3.35
    		O
     
    10
    		](OH)
     
    2
    71.2.2.13Aspidolite
    NaMg
     
    3
    		[(OH)
     
    2
    		|AlSi
     
    3
    		O
     
    10
    		]

    Other Names for Glauconite

    Synonyms:
    GlaukonieGreensand
    Other Languages:
    Basque:Glaukonita
    Dutch:Glauconiet
    Esperanto:Glaŭkonito
    French:Glauconite
    German:Glaukonit
    Glauconit
    Hebrew:גלאוקוניט
    Italian:Glauconite
    Lithuanian:Glaukonitas
    Polish:Glaukonit
    Portuguese:Glauconita
    Slovak:Glaukonit
    Spanish:Glauconita
    Swedish:Glaukonit
    Ukrainian:Глауконіт
    Varieties:
    Aluminium-glauconiteMarsyatskiteSoda-Glauconite

    Other Information

    Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

    References for Glauconite

    Reference List:Schneider, H. (1927) A study of glauconite. Journal of Geology: 35: 289-310.

    Hendricks, S.B. & C.S. Ross (1941), Chemical composition and genesis of glauconite and celadonite: American Mineralogist: 26: 683-708.

    Foster, M.D. (1969), Studies of Celadonite and glauconite: USGS PP 614-F, 17 pp.

    Slonimskaya, M.V., G. Besson, L.G. Daynyak, C. Tchoubar, and V.A. Drits (1986), The interpretation of the IR spectra of celadonites and glauconites in the region of OH-stretching frequencies: Clay Minerals: 21: 377-388.

    Dainyak, L.G., and V.A. Drits (1987), Interpretation of Mössbauer spectra of nontronite, celadonite, and glauconite: Clays and Clay Minerals: 35: 363-372.

    Sakharov, B.A., G. Besson, V.A. Drits, M.Y. Kameneva, A.L. SAlyn, and B.B. Smoliar (1990), X-ray study of the nature of stacking faults in the structure of glauconites: Clay Minerals: 25: 419-435.

    Dainyak, L.G., V.A. Drits, and L.M. Heifits (1992), Computer simulation of cagtion distribution in dioctahedral 2:1 layer silicates using IR-data: Application to Mössbauer spectroscopy of a glauconite sample: Clays and Clay Minerals: 40: 470-479.

    Drits, V.A., L.G. Dainyak, F. Muller, G. Besson, and A. Manceau (1997a), Isomorphous cation distribution in celadonites, glauconites and Fe-illites determined by infrared, Mössbauer and EXAFS spectroscopy: Clay Minerals: 32: 153-180.

    Gaines, Richard V., H. Catherine, W. Skinner, Eugene E. Foord, Brian Mason, Abraham Rosenzweig (1997), Dana's New Mineralogy : The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana: 1453.

    Rieder et.al. 1998, Nomenclature of the Micas: IMA Mica Subcommittee report, Canadian Mineralogist 36: 905-912.

    Internet Links for Glauconite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Glauconite in the Natural History Museum (London) online catalogue
  • Glauconite details from Handbook of Mineralogy (PDF)
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    Localities for Glauconite

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