Okayamalite Mineral Data

General Okayamalite Information

Chemical Formula:

Ca2B2SiO7

Composition:

Molecular Weight = 241.86 gm

Calcium 33.14 % Ca 46.37 % CaO

Silicon 11.61 % Si 24.84 % SiO₂

Boron 8.94 % B 28.78 % B₂O₃

Oxygen 46.31 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂B₂SiO₇

Environment:

The boron-dominant analogue of gehlenite. Skarn mineral probably formed by the desilication-dehydroxylation of datolite.

IMA Status:

Approved IMA 1998 (Dana # Added)

Locality:

The Fuka mine, Bicchu-cho, Okayama Prefecture, Japan. Link to MinDat.org Location Data.

Name Origin:

Named after it's locality.

Name Pronunciation:

Okayamalite + Pronunciation

Synonym:

ICSD 89739

IMA1997-002

Okayamalite Image

Images:

Okayamalite

Comments: Intergrowth between crystalline okayamalite (a) and amorphous silica (b). Okayamalite here forms regular lamellae elongated along [001], typically 400 Ã… thick. The grainy area (c) corresponds to the graphite film..
Location: Skarn sample from the Arendal district, Sorlandet, Norway. (AmMin, v85:1508). Scale: See Image.
© American Mineralogist

Okayamalite Crystallography

Axial Ratios:

a:c = 1:0.67664

Cell Dimensions:

a = 7.116, c = 4.815, Z = 2; V = 243.82 Den(Calc)= 3.29

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): 2.655(1), 2.862(0.56), 3.479(0.4),1.92(0.35), 1.644(0.2), 2.128(0.2), 2.23(0.15), 1.726(0.1), 2.25(0.1),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
Keyboard
S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

Giuli G , Bindi L , Bonazzi P , American Mineralogist , 85 (2000) p.1512-1515, Rietveld refinement of okayamalite, Ca2SiB2O7: Structural evidence for the, B/Si ordered distribution

Physical Properties of Okayamalite

Cleavage:

None

Color:

Creamy white.

Density:

3.3

Habit:

Microscopic Crystals - Crystals visible only with microscopes.

Hardness:

5.5 - Knife Blade

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Okayamalite

Gladstone-Dale:

CI meas= 0.016 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.013 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2082,KPDmeas= 0.2076,KC= 0.2109
Ncalc = 1.69 - 1.7

Optical Data:

Uniaxial (-), e=1.67, w=1.7, bire=0.0300.

Calculated Properties of Okayamalite

Electron Density:

Bulk Density (Electron Density)=3.26 gm/cc
note: Specific Gravity of Okayamalite =3.29 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Okayamalite= 4.63 barns/electron
U=PE_Okayamalite x rElectron Density= 15.11 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Okayamalite is Not Radioactive

Okayamalite Classification

Dana Class:

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

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

(55.04.01)Melilite group

55.04.01.01 Akermanite Ca2MgSi2O7 P 42₁m 4 2m

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

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

55.04.01.04 Okayamalite! Ca2B2SiO7 P 42₁m 4 2m

55.04.01.05 Alumoakermanite! (Ca,Na)2(Al,Mg,Fe)(Si2O7) P 42₁m 4 2m

Strunz Class:

09.BB.10 09 - SILICATES (Germanates)

09.B - Sorosilicates

09.BB -Si2O7 groups, without non-tetrahedral anions;

09.BB.10 Akermanite Ca2MgSi2O7 P 42₁m 4 2m

09.BB.10 Cebollite Ca5Al2(SiO4)3(OH)4 Unk Ortho

09.BB.10 Gugiaite Ca2BeSi2O7 P 42₁m 4 2m

09.BB.10 Gehlenite Ca2Al(AlSi)O7 P 42₁m 4 2m

09.BB.10 Jeffreyite (Ca,Na)2(Be,Al)Si2(O,OH)7 C 222₁ 2 2 2

09.BB.10 Hardystonite Ca2ZnSi2O7 P 42₁m 4 2m

09.BB.10 Melilite (Ca,Na)2(Al,Mg,Fe)(Si,Al)2O7 P 42₁m 4 2m

09.BB.10 Okayamalite! Ca2B2SiO7 P 42₁m 4 2m

Other Okayamalite Information

References:

NAME( MinRec) PHYS. PROP.(Eur. J. Min.,Vol.10,1998) OPTIC PROP.(MinRec)

See Also:

Links to other databases for Okayamalite :
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
11 - WWW-MINCRYST

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Ask about Okayamalite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

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

Okayamalite

Ca2B2SiO7
Dana No: 55.04.01.04 Strunz No: 09.BB.10
Locality:

Notes: