Monazite-(La) Mineral Data

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General Monazite-(La) Information

Chemical Formula:

(La,Ce,Nd)PO4

Composition:

Molecular Weight = 239.90 gm

Lanthanum 28.95 % La 33.95 % La₂O₃

Cerium 14.60 % Ce 17.10 % Ce₂O₃

Thorium 4.84 % Th 5.50 % ThO₂

Phosphorus 12.91 % P 29.58 % P₂O₅

Neodymium 12.02 % Nd 14.03 % Nd₂O₃

Oxygen 26.68 % O

______ ______

100.00 % 100.17 % = TOTAL OXIDE

Empirical Formula:

La_0.5Ce_0.25Nd_0.2Th_0.05(PO₄)

Environment:

Granitic pegmatites.

IMA Status:

Approved IMA 1966

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.

Name Pronunciation:

Monazite-(La)

Synonym:

ICSD 79747

PDF 46-1326

Monazite-(La) Image

Images:

Monazite-(La)

Comments: Yellowish crystals of monazite-(La) in a cavity in nephelin-syenite pegmatite.
Location: Kuivchorr Mt, Lovozero Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia. Scale: FOV is 9x7 mm.
© Pavel M. Kartashov

Monazite-(La) 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)= 5.33

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): 3.12(1), 3.31(0.85), 2.15(0.4),

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, La(PO4)

Physical Properties of Monazite-(La)

Cleavage:

{001} Distinct, {100} Indistinct

Color:

Brown, Brown, Yellowish brown, Pink, Yellow.

Density:

4.8 - 5.5, Average = 5.15

Diaphaneity:

Transparent 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

Luster:

Adamantine - Resinous

Streak:

grayish white

Optical Properties of Monazite-(La)

Gladstone-Dale:

CI meas= 0.009 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.042 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1508,KPDmeas= 0.1561,KC= 0.1574
Ncalc = 1.76 - 1.87

Optical Data:

Biaxial (+), a=1.77-1.8, b=1.7705-1.802, g=1.83-1.85, bire=0.0500-0.0600, 2V(Calc)=12-24, 2V(Meas)=12.

Calculated Properties of Monazite-(La)

Electron Density:

Bulk Density (Electron Density)=4.57 gm/cc
note: Specific Gravity of Monazite-(La) =5.15 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_{Monazite-(La)}= 402.34 barns/electron
U=PE_{Monazite-(La)} x r_electron=1,839.70 barns/cc.

Radioactivity:

GRapi = 91,600.36 (Gamma Ray American Petroleum Institute Units)
Concentration of Monazite-(La) per GRapi unit = 10.92 (PPM)

Monazite-(La) 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) 332.06 ± 83.01 grams of pure Monazite-(La) .

**Estimated Radioactivity from Monazite-(La)** - 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	2,166,567	5.86E-05	91,600.36	30.12
100 gm / 3.33 cm	216,657	5.86E-06	9,160.04	3.01
10 gm / 1.55 cm	21,666	5.86E-07	916.00	0.30
1 gm / 7.18 mm	2,167	5.86E-08	91.60	0.03
0.1 gm / 3.33 mm	217	5.86E-09	9.16	0.00
0.01 gm / 1.55 mm	22	5.86E-10	0.92	0.00
0.001 gm / 0.72 mm	2	5.86E-11	0.09	0.00

Weight of pure Monazite-(La) 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-(La) Classification

Dana Class:

38.04.03.02 (38)Anhydrous Phosphates, etc

(38.04)A+ XO4

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

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

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

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

38.04.03.04 Brabantite? CaTh(PO4)2 P 2₁ 2

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

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

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

Strunz Class:

08.AD.50 08 - PHOSPHATES, ARSENATES, VANADATES

08.A - Phosphates, etc. without additional anions, without H2O

08.AD -With only large cations

08.AD.50 Brabantite? CaTh(PO4)2 P 2₁ 2

08.AD.50 Gasparite-(Ce) CeAsO4 P 2₁/n 2/m

08.AD.50 Monazite-(Ce) (Ce,La,Nd,Th)PO4 P 2₁/n 2/m

08.AD.50 Monazite-(La) (La,Ce,Nd)PO4 P 2₁/n 2/m

08.AD.50 Monazite-(Nd) (Nd,Ce,La)(P,Si)O4 P 2₁/n 2/m

08.AD.50 Rooseveltite BiAsO4 P 2/m 2/m

08.AD.50 Monazite-(Sm)! SmPO4 P 2₁/n 2/m

Other Monazite-(La) Information

References:

NAME( Sinkankas66) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)

See Also:

Links to other databases for Monazite-(La) :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - MinMax(Deutsch)
8 - MinMax(English)
9 - Mineralienatlas (Deutsch)
10 - QUT Mineral Atlas
11 - Ruff.Info
12 - Uranium Minerals

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Print or Cut-and-Paste your Monazite-(La) Specimen Label here :

Monazite-(La)

(La,Ce,Nd)PO4
Dana No: 38.04.03.02 Strunz No: 08.AD.50
Locality:

Notes: