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Griffithite Mineral Data
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General Griffithite Information
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 Chemical Formula: |
4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O) |
| Composition: |
Molecular Weight = 764.30 gm |
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Calcium 2.10 % Ca 2.93 % CaO |
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Magnesium 7.63 % Mg 12.66 % MgO |
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Aluminum 5.30 % Al 10.01 % Al2O3 |
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Iron 12.42 % Fe 11.28 % FeO / 5.22 % Fe2O3 |
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Silicon 18.37 % Si 39.31 % SiO2 |
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Hydrogen 1.85 % H 16.50 % H2O |
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Oxygen 52.33 % O |
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______ ______ |
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100.00 % 97.91 % = TOTAL OXIDE |
| Empirical Formula: |
Mg2.4Fe2+1.2Ca0.4Al1.5Fe3+0.5Si5O18�7(H2O) |
| Environment: |
Amygdaloidal cavities in basalt. A variety of ferroan saponite. |
| IMA Status: |
Not Approved IMA |
| Locality: |
Cahuenga Pass, Griffith Park, Los Angeles, California, USA. Link to MinDat.org Location Data. |
| Name Origin: |
Named after its locality. |
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Griffithite Crystallography
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| Crystal System: |
Monoclinic |
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Physical Properties of Griffithite
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| Cleavage: |
{001} Perfect |
| Color: |
Dark green. |
| Density: |
2.31 |
| Diaphaneity: |
Subtransparent to subtranslucent |
| Habit: |
Platy - Sheet forms (e.g. micas). |
| Hardness: |
1 - Talc |
| Luminescence: |
Non-fluorescent. |
| Luster: |
Vitreous - Dull |
| Magnetism: |
Magnetic after heating |
| Streak: |
green |
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Optical Properties of Griffithite
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| Gladstone-Dale: |
CI meas= -0.028 (Excellent) - where the CI = (1-KPDmeas/KC)
KPDmeas= 0.2341,KC= 0.2277
Ncalc = 1.53 |
| Optical Data: |
Biaxial (-), a=1.485, b=1.565, g=1.572, bire=0.0870 |
| Pleochroism (x): |
pale yellow. |
| Pleochroism (y): |
olive green. |
| Pleochroism (z): |
brownish green. |
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Calculated Properties of Griffithite
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| Electron Density: |
Bulk Density (Electron Density)=2.32 gm/cc
note: Specific Gravity of Griffithite =2.31 gm/cc.
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| Fermion Index: |
Fermion Index = 0.01
Boson Index = 0.99 |
| Photoelectric: |
PEGriffithite = 4.93 barns/electron
U=PEGriffithite x rElectron Density= 11.46 barns/cc.
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| Radioactivity: |
GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Griffithite is Not Radioactive |
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Griffithite Classification
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| Dana Class: |
71.00.00.00 (71)Phyllosilicate Minerals |
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(71.00)Without Dana Classification Numbers |
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(71.00.00)Chlorite Group |
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71.00.00.00 Bariumbannisterite* (K,H3O)(Ba,Ca)(Mn,Fe,Mg)21(Si,Al)32O80(O,OH)16•4-12(H2O) Mono |
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71.00.00.00 Ekmanite? (Fe,Mg,Mn,Fe)3(Si,Al)4O10(OH)2•2(H2O) Unk Ortho |
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71.00.00.00 Griffithite* 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O) Mono |
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71.00.00.00 Orlovite KLi2TiSi4O11F C 2 2 |
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71.00.00.00 Shlykovite KCa[Si4O9(OH)]•3H2O P 21/c 2/m |
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71.00.00.00 Spodiophyllite? (Na,K)4(Mg,Fe)3(Fe,Al)2(Si8O24) Mono |
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71.00.00.00 Voloshinite Rb(LiAl1.5[]0.5)(Al0.5Si3.5)O10F2 C 2/c 2/m |
| Strunz Class: |
09.EC.45 09 - SILICATES (Germanates) |
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09.E - Phyllosilicates |
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09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets |
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09.EC.45 Griffithite* 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O) Mono |
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09.EC.45 Hectorite Na0,3(Mg,Li)3Si4O10(OH)2 C 2/m 2/m |
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09.EC.45 Swinefordite (Li,Ca0.5,Na)0.72(Li,Al,Mg)2.66(Si,Al)4O10(OH,F)2•2(H2O) C 2/m (MON or ORTH) 2/m |
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09.EC.45 Zincsilite Zn3Si4O10(OH)2•4(H2O)(?) C 2/m ? 2/m |
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09.EC.45 Saponite (Ca/2,Na)0,3(Mg,Fe)3(Si,Al)4O10(OH)2•4(H2O) C 2/m 2/m |
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09.EC.45 Sauconite Na0,3Zn3(Si,Al)4O10(OH)2•4(H2O) C 2/m 2/m |
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09.EC.45 Spadaite MgSiO2(OH)2•(H2O)(?) Ortho |
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09.EC.45 Sobotkite? (K,Ca0.5)0.33(Mg,Al)3(Si3Al)O10(OH)2•1-5(H2O) Unk. Mono |
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09.EC.45 Stevensite (Ca0.5,Na)0.33(Mg,Fe)3Si4O10(OH)2•n(H2O) Unk (ORTH ?) Mono |
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09.EC.45 Ferrosaponite! Ca0.3(Fe,Mg,Fe)3(Si,Al)4O10(OH)2•4(H2O) C? Mono |
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Other Griffithite Information
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| References: |
NAME( Ford32) PHYS. PROP.(Dana) OPTIC PROP.(Ford32) |
| See Also: |
Links to other databases for Griffithite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info
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Print or Cut-and-Paste your Griffithite Specimen Label here :
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Griffithite
4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O)
Dana No: 71.00.00.00 Strunz No: 09.EC.45
Locality:
Notes:
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