Stillwellite-(Ce) Mineral Data

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General Stillwellite-(Ce) Information

Chemical Formula:

(Ce,La,Ca)BSiO5

Composition:

Molecular Weight = 245.85 gm

Calcium 0.33 % Ca 0.46 % CaO

Lanthanum 16.95 % La 19.88 % La₂O₃

Cerium 28.50 % Ce 33.38 % Ce₂O₃

Silicon 11.42 % Si 24.44 % SiO₂

Boron 4.40 % B 14.16 % B₂O₃

Neodymium 5.87 % Nd 6.84 % Nd₂O₃

Oxygen 32.54 % O

______ ______

100.00 % 99.15 % = TOTAL OXIDE

Empirical Formula:

Ce_0.5La_0.3Nd_0.1Ca_0.02BSiO₅

Environment:

Metasomatic replacement of metamorphosed calcareous sediments and alkalic pegmatites in syenite.

IMA Status:

Valid Species (Pre-IMA) 1955

Locality:

Mary Kathleen mine, 55 km east of Mt. Isa, Queensland, Australia. Link to MinDat.org Location Data.

Name Origin:

Named for Frank Leslie Stillwell (1888-1963), Australian ore mineralogist and the dominant Ce content.

Name Pronunciation:

Stillwellite-(Ce) + Pronunciation

Synonym:

ICSD 67685

PDF 26-349

Stillwellite-(Ce) Image

Images:

Stillwellite-(Ce)

Comments: Brownish red euhedral crystal of stillwellite-(Ce) in matrix under halogen or sunlight lighting. Inset image shows the yellow color-change under fluorescent lighting.
Location: Darai -Piez Massif, Alay Range of Tien-Shan' Mountains, Garm Region, Tajikistan. Scale: Crystal Size 1.3 cm.
© Rob Lavinsky

Stillwellite-(Ce) Crystallography

Axial Ratios:

a:c = 1:0.97895

Cell Dimensions:

a = 6.844, c = 6.7, Z = 3; V = 271.79 Den(Calc)= 4.51

Crystal System:

Trigonal - PyramidalH-M Symbol (3) Space Group: P 3₁

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

By Intensity(I/I_o): 2.943(1), 3.445(0.9), 4.48(0.9),

Crystal Structure:

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Burns P C , Hawthorne F C , MacDonald D J , Ventura G D , Parodi G , The Canadian Mineralogist , 31 (1993) p.147-152, The crystal structure of stillwellite

Physical Properties of Stillwellite-(Ce)

Cleavage:

{???} Imperfect

Color:

Red brown, Pale pink.

Density:

4.57 - 4.6, Average = 4.58

Diaphaneity:

Transparent to Translucent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Rhombohedral Crystals - Occurs as well-formed crystals showing rhobohedral crystals.

Hardness:

6.5 - Pyrite

Luster:

Resinous

Streak:

white

Optical Properties of Stillwellite-(Ce)

Gladstone-Dale:

CI meas= -0.005 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.021 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1727,KPDmeas= 0.1699,KC= 0.1691
Ncalc = 1.76 - 1.78

Optical Data:

Uniaxial (+), w=1.765-1.784, e=1.78-1.787, bire=0.0030-0.0150.

Calculated Properties of Stillwellite-(Ce)

Electron Density:

Bulk Density (Electron Density)=4.16 gm/cc
note: Specific Gravity of Stillwellite-(Ce) =4.59 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_{Stillwellite-(Ce)}= 259.85 barns/electron
U=PE_{Stillwellite-(Ce)} x r_electron=1,080.70 barns/cc.

Radioactivity:

GRapi = 49,647.95 (Gamma Ray American Petroleum Institute Units)
Concentration of Stillwellite-(Ce) per GRapi unit = 20.14 (PPM)

Stillwellite-(Ce) is Radioactive as defined in 49 CFR 173.403. Greater than 70 Bq / gram.

Estimated Maximum U.S. Postal Shipping Size (10 mRem/hr limit, Unshielded 10 cm box) 612.65 ±153.16 grams of pure Stillwellite-(Ce) .

**Estimated Radioactivity from Stillwellite-(Ce)** - weak
Specimen Size Weight/Volume (Sphere) *	Calculated Activity Bequerols (Bq)	Calculated Activity Curies (Ci)	Estimated Activity GR(api)	Estimated Exposure (mRem**)/hr If Held in Hand For One Hour
1000 gm / 7.47 cm	1,149,426	3.11E-05	49,647.95	16.32
100 gm / 3.47 cm	114,943	3.11E-06	4,964.79	1.63
10 gm / 1.61 cm	11,494	3.11E-07	496.48	0.16
1 gm / 7.47 mm	1,149	3.11E-08	49.65	0.02
0.1 gm / 3.47 mm	115	3.11E-09	4.96	0.00
0.01 gm / 1.61 mm	11	3.11E-10	0.50	0.00
0.001 gm / 0.75 mm	1	3.11E-11	0.05	0.00

Weight of pure Stillwellite-(Ce) in grams (gm) and Calculated Diameter of a Sphere with a Density of 4.59 gm/cc.*
Goverment Estimate of Average Annual Exposure ( 360 mRem) **
Note: 10 microsieverts/hr = 1 mRem/hr **
Max Permissable Adult Dose 50,000 mRem/yr (hands), 15,000 mRem/yr (eyes)
Lethal Dose LD(50) Exposure 400,000 to 500,000 mRem
Estimated Thorium Activity ( 2.57 % Th) From Sum REE Elements (51.31 % REE)

Stillwellite-(Ce) Classification

Dana Class:

54.02.03.02 (54)Nesosilicate Borosilicates and Some Beryllosilicates

(54.02)with B in [4] coordination

(54.02.03)Cappellanite - Stillwellite group

54.02.03.01 Cappelenite-(Y) Ba(Y,Ce)6Si3B6O24F2 P 3 3

54.02.03.02 Stillwellite-(Ce) (Ce,La,Ca)BSiO5 P 3₁ 3

Strunz Class:

09.AJ.25 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AJ -Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra,

09.AJ.25 Stillwellite-(Ce) (Ce,La,Ca)BSiO5 P 3₁ 3

Other Stillwellite-(Ce) Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(AntBidBlaNic2) OPTIC PROP.(AntBidBlaNic2)

See Also:

Links to other databases for Stillwellite-(Ce) :
1 - Alkali-Nuts(English)
2 - Alkali-Nuts(Francais)
3 - Am. Min. Crystal Structure Database
4 - Athena
5 - EUROmin Project
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST

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Print or Cut-and-Paste your Stillwellite-(Ce) Specimen Label here :

Stillwellite-(Ce)

(Ce,La,Ca)BSiO5
Dana No: 54.02.03.02 Strunz No: 09.AJ.25
Locality:

Notes: