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 % B2 O3
Oxygen 46.31 % O
______ ______
100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula:
Ca2 B2 SiO7
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 Å 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 - Scalenohedral H-M Symbol (4 2m) Space Group: P 4 21 m
X Ray Diffraction:
By Intensity(I/Io ): 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),
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:
PEOkayamalite = 4.63 barns/electronU=PEOkayamalite x r Electron 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 4 21 m 4 2m
55.04.01.02 Gehlenite Ca2Al(AlSi)O7 P 4 21 m 4 2m
55.04.01.03 Melilite (Ca,Na)2(Al,Mg,Fe)(Si,Al)2O7 P 4 21 m 4 2m
55.04.01.04 Okayamalite ! Ca2B2SiO7 P 4 21 m 4 2m
55.04.01.05 Alumoakermanite ! (Ca,Na)2(Al,Mg,Fe)(Si2O7) P 4 21 m 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 4 21 m 4 2m
09.BB.10 Cebollite Ca5Al2(SiO4)3(OH)4 Unk Ortho
09.BB.10 Gugiaite Ca2BeSi2O7 P 4 21 m 4 2m
09.BB.10 Gehlenite Ca2Al(AlSi)O7 P 4 21 m 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 4 21 m 4 2m
09.BB.10 Melilite (Ca,Na)2(Al,Mg,Fe)(Si,Al)2O7 P 4 21 m 4 2m
09.BB.10 Okayamalite ! Ca2B2SiO7 P 4 21 m 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
Search for Okayamalite using:
[AOL ]
[Bing ]
[Dog Pile ]
[GeoScienceWorld ]
[HotBot ]
[Ixquick ]
[Lycos ]
[MAMMA ]
[Scirus ]
[Teoma ]
[WebCrawler ]
[Wikipedia ]
[YAHOO ]
Visit our Advertisers for Okayamalite :
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
Espa�ol
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:
Dakota Matrix
Excalibur Minerals
Exceptional Minerals
Hudson Insitute
John Betts Fine Minerals
Mc Dougall Minerals
Mineral News
Rock and Mineral Shows
Weinrich Minerals, Inc.