Mineralogy Database

Griffithite Mineral Data

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General Griffithite Information

Help on Chemical  Formula: Chemical Formula: 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O)
Help on Composition: Composition: Molecular Weight = 764.30 gm
   Calcium     2.10 %  Ca    2.93 % CaO
   Magnesium   7.63 %  Mg   12.66 % MgO
   Aluminum    5.30 %  Al   10.01 % Al2O3
   Iron       12.42 %  Fe   11.28 % FeO /  5.22 % Fe2O3
   Silicon    18.37 %  Si   39.31 % SiO2
   Hydrogen    1.85 %  H    16.50 % H2O
   Oxygen     52.33 %  O
             ______        ______ 
             100.00 %       97.91 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Mg2.4Fe2+1.2Ca0.4Al1.5Fe3+0.5Si5O18�7(H2O)
Help on Environment: Environment: Amygdaloidal cavities in basalt. A variety of ferroan saponite.
Help on IMA Status: IMA Status: Not Approved IMA
Help on Locality: Locality: Cahuenga Pass, Griffith Park, Los Angeles, California, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named after its locality.

Griffithite Crystallography

Help on Crystal System: Crystal System: Monoclinic

Physical Properties of Griffithite

Help on Cleavage: Cleavage: {001} Perfect
Help on Color: Color: Dark green.
Help on Density: Density: 2.31
Help on Diaphaneity: Diaphaneity: Subtransparent to subtranslucent
Help on Habit: Habit: Platy - Sheet forms (e.g. micas).
Help on Hardness: Hardness: 1 - Talc
Help on Luminescence: Luminescence: Non-fluorescent.
Help on Luster: Luster: Vitreous - Dull
Help on Magnetism: Magnetism: Magnetic after heating
Help on Streak: Streak: green

Optical Properties of Griffithite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.028 (Excellent) - where the CI = (1-KPDmeas/KC)
KPDmeas= 0.2341,KC= 0.2277
Ncalc = 1.53
Help on Optical Data: Optical Data: Biaxial (-), a=1.485, b=1.565, g=1.572, bire=0.0870
Help on Pleochroism (x): Pleochroism (x): pale yellow.
Help on Pleochroism (y): Pleochroism (y): olive green.
Help on Pleochroism (z): Pleochroism (z): brownish green.

Calculated Properties of Griffithite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.32 gm/cc
note: Specific Gravity of Griffithite =2.31 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.01
Boson Index = 0.99
Help on Photoelectric: Photoelectric: PEGriffithite = 4.93 barns/electron
U=PEGriffithite x rElectron Density= 11.46 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Griffithite is Not Radioactive

Griffithite Classification

Help on  Dana Class: Dana Class: (71)Phyllosilicate Minerals
  (71.00)Without Dana Classification Numbers
  (71.00.00)Chlorite Group Bariumbannisterite* (K,H3O)(Ba,Ca)(Mn,Fe,Mg)21(Si,Al)32O80(O,OH)16•4-12(H2O) Mono Ekmanite? (Fe,Mg,Mn,Fe)3(Si,Al)4O10(OH)2•2(H2O) Unk Ortho Griffithite* 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O) Mono Orlovite KLi2TiSi4O11F C 2 2 Shlykovite KCa[Si4O9(OH)]•3H2O P 21/c 2/m Spodiophyllite? (Na,K)4(Mg,Fe)3(Fe,Al)2(Si8O24) Mono Voloshinite Rb(LiAl1.5[]0.5)(Al0.5Si3.5)O10F2 C 2/c 2/m
Help on  Strunz Class: Strunz Class: 09.EC.45 09 - SILICATES (Germanates)
  09.E - Phyllosilicates
  09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
09.EC.45 Griffithite* 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2•7(H2O) Mono
09.EC.45 Hectorite Na0,3(Mg,Li)3Si4O10(OH)2 C 2/m 2/m
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
09.EC.45 Zincsilite Zn3Si4O10(OH)2•4(H2O)(?) C 2/m ? 2/m
09.EC.45 Saponite (Ca/2,Na)0,3(Mg,Fe)3(Si,Al)4O10(OH)2•4(H2O) C 2/m 2/m
09.EC.45 Sauconite Na0,3Zn3(Si,Al)4O10(OH)2•4(H2O) C 2/m 2/m
09.EC.45 Spadaite MgSiO2(OH)2•(H2O)(?) Ortho
09.EC.45 Sobotkite? (K,Ca0.5)0.33(Mg,Al)3(Si3Al)O10(OH)2•1-5(H2O) Unk. Mono
09.EC.45 Stevensite (Ca0.5,Na)0.33(Mg,Fe)3Si4O10(OH)2•n(H2O) Unk (ORTH ?) Mono
09.EC.45 Ferrosaponite! Ca0.3(Fe,Mg,Fe)3(Si,Al)4O10(OH)2•4(H2O) C? Mono

Other Griffithite Information

Help on References: References: NAME( Ford32) PHYS. PROP.(Dana) OPTIC PROP.(Ford32)
Help on See Also: 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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Dana No: Strunz No: 09.EC.45





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