Monazite-(Ce) Mineral Data

Monazite-(Ce) Mineral Data +

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General Monazite-(Ce) Information

Chemical Formula:

(Ce,La,Nd,Th)PO4

Composition:

Molecular Weight = 240.21 gm

Lanthanum 14.46 % La 16.95 % La₂O₃

Cerium 29.17 % Ce 34.16 % Ce₂O₃

Thorium 4.83 % Th 5.50 % ThO₂

Phosphorus 12.89 % P 29.55 % P₂O₅

Neodymium 12.01 % Nd 14.01 % Nd₂O₃

Oxygen 26.64 % O

______ ______

100.00 % 100.17 % = TOTAL OXIDE

Empirical Formula:

Ce_0.5La_0.25Nd_0.2Th_0.05(PO₄)

Environment:

Granitic pegmatites.

IMA Status:

Valid Species (Pre-IMA) 1829

Locality:

Mars Hill, Madison County, North Carolina. Link to MinDat.org Location Data.

Name Origin:

From the Greek monazeis - "to be alone" in allusion to its isolated crystals and their rarity when first found.

Synonym:

ICSD 79746

PDF 32-199

Monazite-(Ce) Image

Images:

Monazite-(Ce)

Comments: Orange crystals of monazite-(Ce) on lepidolite.
Location: Conselheiro Pena, Minas Gerais, Brazil. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Monazite-(Ce) Crystallography

Axial Ratios:

a:b:c =0.9686:1:0.9215

Cell Dimensions:

a = 6.79, b = 7.01, c = 6.46, Z = 4; beta = 103.633° V = 298.82 Den(Calc)= 5.34

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/n

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

By Intensity(I/I_o): 2.862(1), 3.078(0.8), 1.963(0.5),

Forms:

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Forms: [ 0 1 0] [ 1 1 1] [ 1 0 1] [ 1 1 0] [ 1 0 0] [ 1 0 1]

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Crystal Structure:

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Ni Y , Hughes J M , Mariano A N , American Mineralogist , 80 (1995) p.21-26, Crystal chemistry of the monazite and xenotime structures

View Additional jPOWD Structure files for Monazite-(Ce)
[1]

Physical Properties of Monazite-(Ce)

Cleavage:

[001] Distinct, [100] Indistinct

Color:

Brown, Colorless, Greenish, Gray white, Yellow.

Density:

4.8 - 5.5, Average = 5.15

Diaphaniety:

Subtransparent to subtranslucent

Fracture:

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

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Habit:

Twinning Common - Crystals are usually twinned.

Hardness:

5-5.5 - Apatite-Knife Blade

Luminescence:

None.

Luster:

Adamantine - Resinous

Streak:

grayish white

Optical Properties of Monazite-(Ce)

Gladstone-Dale:

CI meas= -0.003 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.032 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1517,KPDmeas= 0.1572,KC= 0.1567

Optical Data:

Biaxial (+), a=1.785-1.8, b=1.787-1.801, g=1.837-1.849, bire=0.0490-0.0520, 2V(Calc)=18-24, 2V(Meas)=6-25. Dispersion r > v or r < v.

Pleochroism (x):

colorless or light yellow.

Pleochroism (y):

colorless or dark yellow.

Pleochroism (z):

colorless or greenish yellow.

Calculated Properties of Monazite-(Ce)

Electron Density:

r_electron=4.58 gm/cc
note: r_{Monazite-(Ce)}=5.15 gm/cc.

Fermion Index

Fermion Index = 0.02485
Boson Index = 0.97515

Photoelectric:

PE_{Monazite-(Ce)}= 407.22 barns/electron
U=PE_{Monazite-(Ce)} x r_electron=1,864.04 barns/cc.

Radioactivity:

GRapi = 91,584.19 (Gamma Ray American Petroleum Institute Units)

Monazite-(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) 332.12 ± 83.03 grams of pure Monazite-(Ce) .

**Estimated Radioactivity from Monazite-(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 / 7.18 cm	2,163,836	5.85E-05	91,584.19	30.11
100 gm / 3.33 cm	216,384	5.85E-06	9,158.42	3.01
10 gm / 1.55 cm	21,638	5.85E-07	915.84	0.30
1 gm / 7.18 mm	2,164	5.85E-08	91.58	0.03
0.1 gm / 3.33 mm	216	5.85E-09	9.16	0.00
0.01 gm / 1.55 mm	22	5.85E-10	0.92	0.00
0.001 gm / 0.72 mm	2	5.85E-11	0.09	0.00

Weight of pure Monazite-(Ce) in grams (gm) and Calculated Diameter of a Sphere with a Density of 5.15 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

Monazite-(Ce) Classification

Dana Class:

38.4.3.1 (38)Anhydrous Phosphates, etc

(38.4)A+ XO4

(38.4.3)Monazite Group (Monoclinic: P21/n)

38.4.3.1 Monazite-(Ce) (Ce,La,Nd,Th)PO4 P 2₁/n 2/m

38.4.3.2 Monazite-(La) (La,Ce,Nd)PO4 P 2₁/n 2/m

38.4.3.3 Cheralite-(Ce) (Ce,Ca,Th)(P,Si)O4 P 2₁/n 2/m

38.4.3.4 Brabantite CaTh(PO4)2 P 2₁ 2

38.4.3.5 Monazite-(Nd) (Nd,Ce,La)(P,Si)O4 P 2₁/n 2/m

38.4.3.6 Gasparite-(Ce) CeAsO4 P 2₁/n 2/m

38.4.3.7 Monazite-(Sm)! SmPO4 P 2₁/n 2/m

Strunz Class:

VII/A.15-20 VII - Phosphates, Arsenates and Vanadates

VII/A - Waterfree phosphates [PO4]3- without unfamiliar anions, cations of very big size: Ca, Na and andre

VII/A.15 - Monazite group

VII/A.15-10 Monazite-(La) (La,Ce,Nd)PO4 P 2₁/n 2/m

VII/A.15-20 Monazite-(Ce) (Ce,La,Nd,Th)PO4 P 2₁/n 2/m

VII/A.15-30 Monazite-(Nd) (Nd,Ce,La)(P,Si)O4 P 2₁/n 2/m

VII/A.15-35 Monazite-(Sm)! SmPO4 P 2₁/n 2/m

VII/A.15-40 Cheralite-(Ce) (Ce,Ca,Th)(P,Si)O4 P 2₁/n 2/m

VII/A.15-50 Brabantite CaTh(PO4)2 P 2₁ 2

Other Monazite-(Ce) Information

References:

NAME( Sinkankas66) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Monazite-(Ce)

(Ce,La,Nd,Th)PO4
Dana No: 38.4.3.1 Strunz No: VII/A.15-20
Locality:

Notes: