Gehlenite Mineral Data

Gehlenite Mineral Data +

General Gehlenite Information

Chemical Formula:

Ca2Al(AlSi)O7

Composition:

Molecular Weight = 274.20 gm

Calcium 29.23 % Ca 40.90 % CaO

Aluminum 19.68 % Al 37.18 % Al₂O₃

Silicon 10.24 % Si 21.91 % SiO₂

Oxygen 40.84 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂Al₂SiO₇

Environment:

Contact metamorphic mineral in limestone.

IMA Status:

Valid Species (Pre-IMA) 1815

Locality:

Trentino, Italy. Link to MinDat.org Location Data.

Name Origin:

Named after the German chemist, A. F. Gehlen (1775-1815).

Synonym:

ICSD 39921

PDF 35-755

Gehlenite Image

Images:

Gehlenite

Comments: Crystalline massive gehlenite.
Location: Crestmore Quarry, Riverside County, California, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Gehlenite

Comments: Contact area between vesuvianite (right) and gehlenite (left). Note the lamellae of clintonite included mainly in the gehlenite crystals (CanMin v. 41. p 1259).
Location: Skarns along the contact of a diorite intrusion at Oravit?a, Banat, in Romania. Scale: Image size 2.7 mm.
© Canadian Mineralogist

Gehlenite Crystallography

Axial Ratios:

a:c = 1:0.6589

Cell Dimensions:

a = 7.69, c = 5.067, Z = 2; V = 299.64 Den(Calc)= 3.04

Crystal System:

Tetragonal - ScalenohedralH-M Symbol (4 2m) Space Group: P 42₁m

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

By Intensity(I/I_o): 1.75(1), 2.85(1), 2.43(0.7),

Crystal Structure:

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Louisnathan S J , The Canadian Mineralogist , 10 (1971) p.822-837, Refinement of the crystal structure of a natural gehlenite, Ca2Al(Al,Si)2O7

View Additional jPOWD Structure files for Gehlenite
[1] [2]

Physical Properties of Gehlenite

Cleavage:

[001] Good

Color:

Brown, Colorless, Greenish, Gray, Yellow.

Density:

2.9 - 3.07, Average = 2.98

Diaphaniety:

Transparent to translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

5-6 - Between Apatite and Orthoclase

Luster:

Vitreous - Greasy

Streak:

white

Optical Properties of Gehlenite

Gladstone-Dale:

CI meas= -0.069 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= -0.049 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2188,KPDmeas= 0.2228,KC= 0.2084

Optical Data:

Uniaxial (-), e=1.66, w=1.67, bire=0.0100.

Calculated Properties of Gehlenite

Electron Density:

r_electron=3.02 gm/cc
note: r_Gehlenite=3.04 gm/cc.

Fermion Index

Fermion Index = 0.00537
Boson Index = 0.99463

Photoelectric:

PE_Gehlenite= 4.57 barns/electron
U=PE_Gehlenite x r_electron= 13.77 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Gehlenite is Not Radioactive

Gehlenite Classification

Dana Class:

55.4.1.2 (55)Sorosilicate Si2O7 Groups, Generally with No Additional Anions

(55.4)with cations in [8] and lower coordination

(55.4.1)Melilite group

55.4.1.1 Akermanite Ca2MgSi2O7 P 42₁m 4 2m

55.4.1.2 Gehlenite Ca2Al(AlSi)O7 P 42₁m 4 2m

55.4.1.3 Melilite (Ca,Na)2(Al,Mg,Fe)(Si,Al)2O7 P 42₁m 4 2m

55.4.1.4 Okayamalite! Ca2B2SiO7 P 42₁m 4 2m

Strunz Class:

VIII/C.02-15 VIII - Silicates

VIII/C - Sorosilicates, with [Si2O7]6-, without anions unfamiliar to tetraheders

VIII/C.02 - Melilite group

VIII/C.02-10 Akermanite Ca2MgSi2O7 P 42₁m 4 2m

VIII/C.02-14 Okayamalite! Ca2B2SiO7 P 42₁m 4 2m

VIII/C.02-15 Gehlenite Ca2Al(AlSi)O7 P 42₁m 4 2m

VIII/C.02-30 Gugiaite Ca2BeSi2O7 P 42₁m 4 2m

VIII/C.02-40 Hardystonite Ca2ZnSi2O7 P 42₁m 4 2m

VIII/C.02-50 Leucophanite (Na,Ca)2BeSi2(O,OH,F)7 P1 1

VIII/C.02-60 Jeffreyite (Ca,Na)2(Be,Al)Si2(O,OH)7 C 222₁ 2 2 2

VIII/C.02-70 Meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] I 4 4

VIII/C.02-80 Barylite BaBe2Si2O7 Pn21a mm2

VIII/C.02-85 Clinobarylite! BaBe2Si2O7 Pmn2 2/m 2/m 2/m

VIII/C.02-90 Andremeyerite BaFe(Fe,Mn,Mg)Si2O7 P 2₁/c 2/m

Other Gehlenite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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

Gehlenite

Ca2Al(AlSi)O7
Dana No: 55.4.1.2 Strunz No: VIII/C.02-15
Locality:

Notes: