Steacyite Mineral Data

Steacyite Mineral Data +

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General Steacyite Information

Chemical Formula:

K1-x(Ca,Na)2ThSi8O20 (x=0.2 to 0.4)

Composition:

Molecular Weight = 825.70 gm

Potassium 2.84 % K 3.42 % K₂O

Sodium 1.95 % Na 2.63 % Na₂O

Calcium 3.40 % Ca 4.75 % CaO

Thorium 25.29 % Th 28.78 % ThO₂

Manganese 1.33 % Mn 1.72 % MnO

Silicon 27.21 % Si 58.21 % SiO₂

Oxygen 37.98 % O

______ ______

100.00 % 99.52 % = TOTAL OXIDE

Empirical Formula:

K_0.6Na_0.7Ca_0.7Mn²⁺_0.2Th_0.9Si₈O_19.6

Environment:

In cavities in pegmatite veins in nepheline syenite.

IMA Status:

Approved IMA 1982

Locality:

Mont Saint-Hilaire, Quebec, Canada. Link to MinDat.org Location Data.

Name Origin:

Named for Harold R. Steacy, formerly Curator of the National Mineral Collection, Geological Survey of Canada, Ottawa, Canada.

Synonym:

Desourdyite

Steacyite Image

Images:

Steacyite

Comments: Square prismatic crystal of steacyite on acicular aegirine.
Location: Mont St. Hilaire, Quebec, Canada. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Steacyite Crystallography

Axial Ratios:

a:c = 1:1.94854

Cell Dimensions:

a = 7.58, c = 14.77, Z = 2; V = 848.63 Den(Calc)= 3.23

Crystal System:

Tetragonal - Ditetragonal DipyramidalH-M Symbol (4/m 2/m 2/m) Space Group: P 4/mcc

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

By Intensity(I/I_o): 3.38(1), 5.22(0.9), 7.32(0.9),

Physical Properties of Steacyite

Cleavage:

None

Color:

Brown, Yellow green.

Density:

2.95

Diaphaniety:

Translucent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Hardness:

5 - Apatite

Luminescence:

Radioactive.

Luster:

Vitreous - Dull

Streak:

white

Optical Properties of Steacyite

Gladstone-Dale:

CI meas= 0.001 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.087 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1772,KPDmeas= 0.1941,KC= 0.1942

Optical Data:

Uniaxial (-), e=1.572, w=1.573, bire=0.0010.

Calculated Properties of Steacyite

Electron Density:

r_electron=2.77 gm/cc
note: r_Steacyite=2.95 gm/cc.

Fermion Index

Fermion Index = 0.01293
Boson Index = 0.98707

Photoelectric:

PE_Steacyite= 568.46 barns/electron
U=PE_Steacyite x r_electron=1,575.62 barns/cc.

Radioactivity:

GRapi = 506,988.44 (Gamma Ray American Petroleum Institute Units)

Steacyite 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) 59.99 ± 15.00 grams of pure Steacyite .
Estimated Maximum U.S. Postal Shipping Size (10 mRem/hr limit, Unshielded 100 cm box) 5999.5 ±1499.9 grams of pure Steacyite .

**Estimated Radioactivity from Steacyite** - strong
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 / 8.65 cm	11,331,574	3.06E-04	506,988.44	166.68
100 gm / 4.02 cm	1,133,157	3.06E-05	50,698.84	16.67
10 gm / 1.86 cm	113,316	3.06E-06	5,069.88	1.67
1 gm / 8.65 mm	11,332	3.06E-07	506.99	0.17
0.1 gm / 4.02 mm	1,133	3.06E-08	50.70	0.02
0.01 gm / 1.86 mm	113	3.06E-09	5.07	0.00
0.001 gm / 0.87 mm	11	3.06E-10	0.51	0.00

Weight of pure Steacyite in grams (gm) and Calculated Diameter of a Sphere with a Density of 2.95 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

Steacyite Classification

Dana Class:

63.1.1.1 (63)Cyclosilicate Condensed Rings

(63.1)Steacyite group (4x2) Double Rings

(63.1.1)Eudialyte subgroup

63.1.1.1 Steacyite K1-x(Ca,Na)2ThSi8O20(x=0.2to0.4) P 4/mcc 4/m 2/m 2/m

63.1.1.2 Iraqite-(La) K(La,Ce,Th)2(Ca,Na)4(Si,Al)16O40 P 4/mcc 4/m 2/m 2/m

63.1.1.3 Turkestanite! Th(Ca,Na)2(K1-x,[]x)Si8O20·n(H2O) P 4/mcc 4/m 2/m 2/m

63.1.1.4 Arapovite! (U,Th)(Ca,Na)2(K1-x[]x)Si8O20,x~0.5 P 4/mcc 4/m 2/m 2/m

Strunz Class:

VIII/E.10-30 VIII - Silicates

VIII/E - Cyklosilicates, double quadruplet rings [Si8O20]8-

VIII/E.10 - Ekanite - Steacyite series

VIII/E.10-10 Ekanite ThCa2Si8O20 I 422 4 2 2

VIII/E.10-20 Iraqite-(La) K(La,Ce,Th)2(Ca,Na)4(Si,Al)16O40 P 4/mcc 4/m 2/m 2/m

VIII/E.10-30 Steacyite K1-x(Ca,Na)2ThSi8O20(x=0.2to0.4) P 4/mcc 4/m 2/m 2/m

VIII/E.10-40 Turkestanite! Th(Ca,Na)2(K1-x,[]x)Si8O20·n(H2O) P 4/mcc 4/m 2/m 2/m

Other Steacyite Information

References:

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

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Steacyite

K1-x(Ca,Na)2ThSi8O20 (x=0.2 to 0.4)
Dana No: 63.1.1.1 Strunz No: VIII/E.10-30
Locality:

Notes: