Glauconite Mineral Data

Glauconite Mineral Data +

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General Glauconite Information

Chemical Formula:

(K,Na)(Fe+++,Al,Mg)2(Si,Al)4O10(OH)2

Composition:

Molecular Weight = 426.93 gm

Potassium 5.49 % K 6.62 % K₂O

Sodium 0.27 % Na 0.36 % Na₂O

Magnesium 2.28 % Mg 3.78 % MgO

Aluminum 1.90 % Al 3.58 % Al₂O₃

Iron 19.62 % Fe 3.37 % FeO / 24.31 % Fe₂O₃

Silicon 25.00 % Si 53.48 % SiO₂

Hydrogen 0.47 % H 4.22 % H₂O

Oxygen 44.97 % O

______ ______

100.00 % 99.72 % = TOTAL OXIDE

Empirical Formula:

K_0.6Na_0.05Fe³⁺_1.3Mg_0.4Fe²⁺_0.2Al_0.3Si_3.8O₁₀(OH)₂

Environment:

Altered from detrital biotite by marine diagenesis in shallow water under reducing conditions; especially in sandstone.

IMA Status:

Valid Species (Pre-IMA) 1828

Locality:

Otago Peninsula, New Zealand. Common world wide. Link to MinDat.org Location Data.

Name Origin:

From the Greek "glaucos" for the blue green color.

Glauconite Image

Images:

Glauconite

Comments: Green glauconite intermixed with quartz.
Location: Ightham, Kent, England. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Glauconite Crystallography

Axial Ratios:

a:b:c =0.5773:1:1.1206

Cell Dimensions:

a = 5.234, b = 9.066, c = 10.16, Z = 2; beta = 100.5° V = 474.03 Den(Calc)= 2.99

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m

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

By Intensity(I/I_o): 10.1(1), 2.59(1), 4.53(0.8),1.511(0.6), 2.396(0.6), 3.33(0.6), 3.63(0.4),

Physical Properties of Glauconite

Cleavage:

[001] Perfect

Color:

Blue green, Green, Yellow green.

Density:

2.4 - 2.95, Average = 2.67

Diaphaniety:

Translucent to Subopaque

Habit:

Micaceous - Platy texture with "flexible" plates.

Hardness:

2 - Gypsum

Luminescence:

Non-fluorescent.

Luster:

Earthy (Dull)

Magnetism:

Nonmagnetic

Streak:

light green

Optical Properties of Glauconite

Gladstone-Dale:

CI meas= -0.001 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.104 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2067,KPDmeas= 0.231,KC= 0.2308

Optical Data:

Biaxial (-), a=1.59-1.612, b=1.609-1.643, g=1.61-1.644, bire=0.0200-0.0320, 2V(Calc)=20-24, 2V(Meas)=0-20. Dispersion r > v.

Pleochroism (x):

lemon yellow, pale yellowish green, or bright green.

Pleochroism (y):

green, dark green, yellowish green, bluish green, or olive green.

Pleochroism (z):

green, dark green, yellowish green, bluish green, or olive green.

Calculated Properties of Glauconite

Electron Density:

r_electron=2.64 gm/cc
note: r_Glauconite=2.68 gm/cc.

Fermion Index

Fermion Index = 0.01833
Boson Index = 0.98167

Photoelectric:

PE_Glauconite= 7.42 barns/electron
U=PE_Glauconite x r_electron= 19.61 barns/cc.

Radioactivity:

GRapi = 78.31 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Glauconite - barely detectable

Glauconite Classification

Dana Class:

71.2.2a.5 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.2)with 2:1 Layers

(71.2.2a)Mica Group (Muscovite subgroup)

71.2.2a.1 Muscovite KAl2(Si3Al)O10(OH,F)2 C 2/m 2/m

71.2.2a.2 Paragonite NaAl2(Si3Al)O10(OH)2 C 2/c,Cc Mono

71.2.2a.3 Chernykhite (Ba,Na)V,Al)2(Si,Al)4O10(OH)2 C 2/c 2/m

71.2.2a.4 Roscoelite K(V,Al,Mg)2AlSi3O10(OH)2 C 2/m 2/m

71.2.2a.5 Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2 C 2/m 2/m

71.2.2a.6 Celadonite K(Mg,Fe)(Fe,Al)[Si4O10](OH)2 C 2/m 2/m

71.2.2a.6b Ferroceladonite! K2FeFeSi8O20(OH)4 C 2/m 2/m

71.2.2a.6c Ferro-aluminoceladonite! K2Fe2Al2Si8O20(OH)4 C 2/m 2/m

71.2.2a.6d Aluminoceladonite! KAl(Mg,Fe)[]Si4O10(OH)2 2/m

71.2.2a.6e Chromceladonite! KCrMg(Si4O10)(OH)2 C 2 2

71.2.2a.7 Tobelite (NH4,K)Al2(Si3Al)O10(OH)2 C 2/m 2/m

71.2.2a.8 Nanpingite Cs(Al,Mg,Fe,Li)2(Si3Al)O10(OH,F)2 C 2/c 2/m

71.2.2a.9 Boromuscovite KAl2(Si3B)O10(OH,F)2 C 2/m 2/m

71.2.2a.10 Montdorite (K,Na)(Fe,Mn,Mg)2.5[Si4O10](F,OH)2 C 2/c 2/m

71.2.2a.11 Chromphyllite! (K,Ba)(Cr,Al)2[AlSi3O10](OH,F)2 C 2c 2/m

71.2.2a.12 Shirokshinite! K(NaMg2)Si4O10F2 C 2/m 2/m

Strunz Class:

VIII/H.13-00 VIII - Silicates

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

VIII/H.13 - Mica group - Glauconite series

Other Glauconite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Glauconite

(K,Na)(Fe+++,Al,Mg)2(Si,Al)4O10(OH)2
Dana No: 71.2.2a.5 Strunz No: VIII/H.13-00
Locality:

Notes: