Brockite Mineral Data

Brockite Mineral Data +

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General Brockite Information

Chemical Formula:

(Ca,Th,Ce)(PO4)·(H2O)

Composition:

Molecular Weight = 220.66 gm

Calcium 10.90 % Ca 15.25 % CaO

Cerium 6.35 % Ce 7.44 % Ce₂O₃

Thorium 31.55 % Th 35.90 % ThO₂

Phosphorus 14.04 % P 32.16 % P₂O₅

Hydrogen 0.91 % H 8.16 % H₂O

Oxygen 36.25 % O

______ ______

100.00 % 98.91 % = TOTAL OXIDE

Empirical Formula:

Ca_0.6Th_0.3Ce_0.1(PO₄)·(H₂O)

Environment:

A rare accessory mineral in granite and granite pegmatites.

IMA Status:

Approved IMA 1962

Locality:

In the USA, in a prospect pit about one km east of the Bassick mine, Querida, Wet Mountains, and at the Hardwick mine and Nightingale shaft, Custer Co., Colorado. Link to MinDat.org Location Data.

Name Origin:

To honor Maurice R. Brock, U.S. Geological Survey, who supplied the first specimen.

Synonym:

Silicosmirnovskite

Smirnovskite

Brockite Image

Images:

Brockite

Comments: Red-brown opaque massive brockite.
Location: Anna Lee Mine, Custer County, Colorado, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Brockite Crystallography

Axial Ratios:

a:c = 1:0.9169

Cell Dimensions:

a = 6.98, c = 6.4, Z = 3; V = 270.04 Den(Calc)= 4.07

Crystal System:

Hexagonal - TrapezohedralH-M Symbol (6 2 2) Space Group: P 6₂22

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

By Intensity(I/I_o): 3.03(1), 2.83(0.7), 4.37(0.7),

Physical Properties of Brockite

Cleavage:

None

Color:

White, Light yellow, Dark reddish brown, Reddish brown.

Density:

3.7 - 4.1, Average = 3.9

Diaphaniety:

Translucent

Fracture:

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

Hardness:

3-4 - Calcite-Fluorite

Luster:

Vitreous - Greasy

Optical Properties of Brockite

Gladstone-Dale:

CI meas= 0.069 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= 0.108 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1689,KPDmeas= 0.1763,KC= 0.1893

Optical Data:

Uniaxial (+), w=1.68, e=1.695, bire=0.0150.

Calculated Properties of Brockite

Electron Density:

r_electron=3.60 gm/cc
note: r_Brockite=3.90 gm/cc.

Fermion Index

Fermion Index = 0.00032
Boson Index = 0.99968

Photoelectric:

PE_Brockite= 753.16 barns/electron
U=PE_Brockite x r_electron=2,710.28 barns/cc.

Radioactivity:

GRapi = 620,988.89 (Gamma Ray American Petroleum Institute Units)

Brockite 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) 48.98 ± 12.25 grams of pure Brockite .
Estimated Maximum U.S. Postal Shipping Size (10 mRem/hr limit, Unshielded 100 cm box) 4898.1 ±1224.5 grams of pure Brockite .

**Estimated Radioactivity from Brockite** - 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 / 7.88 cm	14,133,249	3.82E-04	620,988.89	204.16
100 gm / 3.66 cm	1,413,325	3.82E-05	62,098.89	20.42
10 gm / 1.70 cm	141,332	3.82E-06	6,209.89	2.04
1 gm / 7.88 mm	14,133	3.82E-07	620.99	0.20
0.1 gm / 3.66 mm	1,413	3.82E-08	62.10	0.02
0.01 gm / 1.70 mm	141	3.82E-09	6.21	0.00
0.001 gm / 0.79 mm	14	3.82E-10	0.62	0.00

Weight of pure Brockite in grams (gm) and Calculated Diameter of a Sphere with a Density of 3.90 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

Brockite Classification

Dana Class:

40.4.7.5 (40)Hydrated Phosphates, etc

(40.4)where A+++ XO4 · x(H2O)

(40.4.7)Dana Group

40.4.7.1 Rhabdophane-(Ce) (Ce,La)PO4·(H2O) P 6₂22 6 2 2

40.4.7.2 Rhabdophane-(La) (La,Ce)PO4·(H2O) P 6₂22 6 2 2

40.4.7.3 Rhabdophane-(Nd) (Nd,Ce,La)PO4·(H2O) P 6₂22 6 2 2

40.4.7.4 Grayite (Th,Pb,Ca)PO4·(H2O) P 6₂22 6 2 2

40.4.7.5 Brockite (Ca,Th,Ce)(PO4)·(H2O) P 6₂22 6 2 2

40.4.7.6 Tristramite (Ca,U,Fe)(PO4,SO4)·2(H2O) P 6₂22 6 2 2

Strunz Class:

VII/C.29-40 VII - Phosphates, Arsenates and Vanadates

VII/C - Water-bearing phosphates without unfamiliar anions, cations of medium and big size: Fe, Mn, Zn, Mg and Ca, (NH4)1+

VII/C.29 - Rhabdophane group

VII/C.29-10 Rhabdophane-(Ce) (Ce,La)PO4·(H2O) P 6₂22 6 2 2

VII/C.29-20 Rhabdophane-(La) (La,Ce)PO4·(H2O) P 6₂22 6 2 2

VII/C.29-30 Rhabdophane-(Nd) (Nd,Ce,La)PO4·(H2O) P 6₂22 6 2 2

VII/C.29-40 Brockite (Ca,Th,Ce)(PO4)·(H2O) P 6₂22 6 2 2

VII/C.29-50 Tristramite (Ca,U,Fe)(PO4,SO4)·2(H2O) P 6₂22 6 2 2

VII/C.29-60 Grayite (Th,Pb,Ca)PO4·(H2O) P 6₂22 6 2 2

VII/C.29-70 Ningyoite (U,Ca,Ce)2(PO4)2·1-2(H2O) P 222 2 2 2

Other Brockite Information

References:

NAME( AntBidBlaNic4) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Brockite

(Ca,Th,Ce)(PO4)·(H2O)
Dana No: 40.4.7.5 Strunz No: VII/C.29-40
Locality:

Notes: