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Offretite Mineral Data

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General Offretite Information

Help on Chemical  Formula: Chemical Formula: (K2,Ca,Mg)2.5Al5Si13O36•15(H2O)
Help on Composition: Composition: Molecular Weight = 1,453.72 gm
   Potassium   2.96 %  K     3.56 % K2O
   Calcium     3.03 %  Ca    4.24 % CaO
   Magnesium   1.17 %  Mg    1.94 % MgO
   Aluminum    9.65 %  Al   18.24 % Al2O3
   Silicon    24.73 %  Si   52.90 % SiO2
   Hydrogen    2.11 %  H    18.84 % H2O
   Oxygen     56.35 %  O
             ______        ______ 
             100.00 %       99.72 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: K1.1Ca1.1Mg0.7Al5.2Si12.8O36•15.2(H2O)
Help on Environment: Environment: Alteration of basalt with the addition of potash.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1890
Help on Locality: Locality: Mont Simiouse, near Montbrison, Loire, France. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for Albert Jules Joseph Offret (1857-?), professor in the Faculty of Sciences, Lyon, France.
Help on Name Pronunciation: Name Pronunciation: Offretite + Pronunciation Say OFFRETITE
Help on Synonym: Synonym: ICSD 8292
  PDF 25-1186
 

Offretite Image

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  Offretite

Comments: Clear crystal of offretite on matrix.
Location: Mont Simiouse, near Montbrison, Loire, France. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Offretite Crystallography

Help on Axial Ratios: Axial Ratios: a:c = 1:0.57052
Help on Cell Dimensions: Cell Dimensions: a = 13.307, c = 7.592, Z = 1; V = 1,164.25 Den(Calc)= 2.07
Help on Crystal System: Crystal System: Hexagonal - Ditrigonal Dipyramidal H-M Symbol (6 m2) Space Group: P 6m2
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 11.5(1), 2.88(0.65), 4.35(0.6),
 

Physical Properties of Offretite

Help on Cleavage: Cleavage: {0001} Distinct
Help on Color: Color: Colorless, White.
Help on Density: Density: 2.13
Help on Diaphaneity: Diaphaneity: Transparent to Translucent
Help on Fracture: Fracture: Brittle - Uneven - Very brittle fracture producing uneven fragments.
Help on Habit: Habit: Hexagonal - Six-sided crystal shape in cross-section or habit.
Help on Habit: Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Habit: Habit: Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)
Help on Hardness: Hardness: 4-4.5 - Between Fluorite and Apatite
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: white
 

Optical Properties of Offretite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.006 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.023 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.237,KPDmeas= 0.2303,KC= 0.2316
Ncalc = 1.48 - 1.49
Help on Optical Data: Optical Data: Uniaxial (-), e=1.486-1.492, w=1.489-1.495, bire=0.0030.
 

Calculated Properties of Offretite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.16 gm/cc
note: Specific Gravity of Offretite =2.13 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.01
Boson Index = 0.99
Help on Photoelectric: Photoelectric: PEOffretite = 1.96 barns/electron
U=PEOffretite x relectron= 4.24 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 43.33 (Gamma Ray American Petroleum Institute Units)
Concentration of Offretite per GRapi unit = 2.31 (%)

Estimated Radioactivity from Offretite - barely detectable

 

Offretite Classification

Help on  Dana Class: Dana Class: 77.01.02.04 (77)Tectosilicate Zeolite group
  (77.01)true zeolites
  (77.01.02)Chabazite and related species
 
77.01.02.01 Chabazite-Ca (Ca0.5,Na,K)4[Al4Si8O24]•12H2O P1 1
 
77.01.02.01a Chabazite-Na! (Na2,K2,Ca,Mg)[Al2Si4O12]•6(H2O) R 3m 3 2/m
 
77.01.02.01b Chabazite-K! (K2,Ca,Na2,Mg)[Al2Si4O12]•6(H2O) R 3m 3 2/m
 
77.01.02.01c Chabazite-Sr! (Sr,Ca,K2,Na2)[Al2Si4O12]•6(H2O) R 3m 3 2/m
 
77.01.02.02 Herschelite? (Na,Ca,K)AlSi2O6•3(H2O) R 3m 3 2/m
 
77.01.02.03 Willhendersonite KCaAl3Si3O12•5(H2O) P1 1
 
77.01.02.04 Offretite (K2,Ca,Mg)2.5Al5Si13O36•15(H2O) P 6m2 6 m2
 
77.01.02.05 Erionite-Na (Na2,K2,Ca)2[Al4Si14O36]•15(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.05a Erionite-K! (K2,Ca,Na2)2[Al4Si14O36]•15(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.05b Erionite-Ca! (Ca,K2,Na2)2[Al4Si14O36]•15(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.06 Gmelinite-Na (Na2,Ca)Al2Si4O12•6(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.06a Gmelinite-Ca! (Ca,Na2)Al2Si4O12•6(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.06b Gmelinite-K! (K,Na,Ca)6(Al7Si17O48)•22(H2O) P 63/mmc 6/m 2/m 2/m
 
77.01.02.07 Faujasite-Na (Na2,Ca,Mg)3.5[Al7Si17O48]•32(H2O) F d3m 4/m 3 2/m
 
77.01.02.07a Faujasite-Ca! (Ca,Na2,Mg)3.5[Al7Si17O48]•32(H2O) F d3m 4/m 3 2/m
 
77.01.02.07b Faujasite-Mg! (Mg,Na2,Ca)3.5[Al7Si17O48]•32(H2O) F d3m 4/m 3 2/m
 
77.01.02.08 Levyne-Ca (Ca,Na2,K2)Al2Si4O12•6(H2O) R 3m 3 2/m
 
77.01.02.08a Levyne-Na! (Na2,Ca,K2)Al2Si4O12•6(H2O) R 3m 3 2/m
 
77.01.02.09 Tschortnerite! Ca4(Ca,Sr,K,Ba)3Cu3(OH)8[Si12Al12O48]•x(H2O),x>=20 F m3m 4/m 3 2/m
Help on  Strunz Class: Strunz Class: 09.GD.25 09 - SILICATES (Germanates)
  09.G - Tektosilicates with Zeolitic H2O
  09.GD -Chains of 6-membered rings � tabular zeolites
 
09.GD.25 Offretite (K2,Ca,Mg)2.5Al5Si13O36•15(H2O) P 6m2 6 m2
 
09.GD.25 Wenkite Ba4Ca6(Si,Al)20O39(OH)2(SO4)3•n(H2O)(?) P 62m 6 m2
 

Other Offretite Information

Help on References: References: NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic2)
Help on See Also: See Also: Links to other databases for Offretite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST
16 - Zeolite Database by Bruno Herreros

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Print or Cut-and-Paste your Offretite Specimen Label here :

Offretite

(K2,Ca,Mg)2.5Al5Si13O36•15(H2O)
Dana No: 77.01.02.04 Strunz No: 09.GD.25
Locality:

 

Notes:

 

 
   
 


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