Melilite Mineral Data

Melilite Mineral Data +

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General Melilite Information

Chemical Formula:

(Ca,Na)2(Al,Mg,Fe++)(Si,Al)2O7

Composition:

Molecular Weight = 268.29 gm

Sodium 4.28 % Na 5.78 % Na₂O

Calcium 22.41 % Ca 31.35 % CaO

Magnesium 2.72 % Mg 4.51 % MgO

Aluminum 11.06 % Al 20.90 % Al₂O₃

Iron 2.08 % Fe 2.68 % FeO

Silicon 15.70 % Si 33.59 % SiO₂

Oxygen 41.74 % O

______ ______

100.00 % 98.81 % = TOTAL OXIDE

Empirical Formula:

Ca_1.5Na_0.5Al_1.1Mg_0.3Fe²⁺_0.1Si_1.5O₇

Environment:

Igneous rocks poor in silica and alkalis.

IMA Status:

Valid Species (Pre-IMA) 1796

Locality:

Capo di Bove, near Rome, Italy. Link to MinDat.org Location Data.

Name Origin:

From the Greek, meli - "honey" and lithos - "stone."

Melilite Image

Images:

Melilite

Comments: Barrel-shaped root-beer colored melilite crystal with clear nepheline.
Location: Udersdorf, Rhineland-Palatinate, Germany. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Melilite Monticellite

Comments: Thin-section image of monticellite interstitial between unaltered melilite crystals (CanMin v. 41. p 1259).
Location: Skarns along the contact of a diorite intrusion at Oravit?a, Banat, in Romania. Scale: Field of View 2.7 mm.
© Canadian Mineralogist

Melilite Crystallography

Axial Ratios:

a:c = 1:0.66092

Cell Dimensions:

a = 7.715, c = 5.099, Z = 2; V = 303.50 Den(Calc)= 2.94

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): 2.8577(1), 1.7619(0.27), 3.0791(0.24),

Crystal Structure:

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Smith J V , American Mineralogist , 38 (1953) p.643-661, Reexamination of the crystal structure of melilite

View Additional jPOWD Structure files for Melilite
[1] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Melilite

Cleavage:

[001] Distinct, [100] Indistinct

Color:

White, Yellowish white, Brown, Gray, Greenish gray.

Density:

2.9 - 3, Average = 2.95

Diaphaniety:

Translucent

Fracture:

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

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Habit:

Massive - Lamellar - Distinctly foliated fine-grained forms.

Hardness:

5-5.5 - Apatite-Knife Blade

Luminescence:

None.

Luster:

Vitreous - Greasy

Streak:

white

Optical Properties of Melilite

Dichroism (e):

colorless or light yellow.

Dichroism (w):

colorless or dark yellow.

Gladstone-Dale:

CI meas= -0.074 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= -0.078 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2198,KPDmeas= 0.2191,KC= 0.204

Optical Data:

Uniaxial (-), e=1.626-1.658, w=1.632-1.669, bire=0.0060-0.0110.

Calculated Properties of Melilite

Electron Density:

r_electron=2.92 gm/cc
note: r_Melilite=2.95 gm/cc.

Fermion Index

Fermion Index = 0.01099
Boson Index = 0.98901

Photoelectric:

PE_Melilite= 4.43 barns/electron
U=PE_Melilite x r_electron= 12.95 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Melilite is Not Radioactive

Melilite Classification

Dana Class:

55.4.1.3 (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:

VII/C.02-20 VII - Phosphates, Arsenates and Vanadates

VII/C - Water-bearing phosphates without unfamiliar anions. cations of medium and small size: Be and Mn, Fe, Cu, Zn, Mg

VII/C.02 - Faheyite - Gainesite-(NaCs) series

VII/C.02-10 Faheyite (Mn,Mg)Fe2Be2(PO4)4·6(H2O) P 6₂22 6 2 2

VII/C.02-20 Melilite (Ca,Na)2(Al,Mg,Fe)(Si,Al)2O7 P 42₁m 4 2m

VII/C.02-25 Selwynite NaK(Be,Al)Zr2(PO4)4·2(H2O) I 4₁/amd 4/m 2/m 2/m

VII/C.02-35 Gainesite Na2Zr2Be(PO4)4·1-2(H2O) I 4₁/amd 4/m 2/m 2/m

VII/C.02-40 Mccrillisite NaCs(Be,Li)Zr2(PO4)4·1-2(H2O) I 4₁/amd 4/m 2/m 2/m

Other Melilite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Melilite

(Ca,Na)2(Al,Mg,Fe++)(Si,Al)2O7
Dana No: 55.4.1.3 Strunz No: VII/C.02-20
Locality:

Notes: