Arrojadite Mineral Data

Arrojadite Mineral Data +

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General Arrojadite Information

Chemical Formula:

KNa4CaMn++4Fe++10Al(PO4)12(OH,F)2

Composition:

Molecular Weight = 2,151.01 gm

Potassium 1.82 % K 2.19 % K₂O

Sodium 4.28 % Na 5.76 % Na₂O

Calcium 1.86 % Ca 2.61 % CaO

Manganese 10.22 % Mn 13.19 % MnO

Aluminum 1.25 % Al 2.37 % Al₂O₃

Iron 25.96 % Fe 33.40 % FeO

Phosphorus 17.28 % P 39.59 % P₂O₅

Hydrogen 0.07 % H 0.63 % H₂O

Oxygen 36.82 % O

Fluorine 0.44 % F 0.44 % F

- % F -0.19 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

KNa₄CaMn²⁺₄Fe²⁺₁₀Al(PO₄)₁₂(OH)_1.5F_0.5

Environment:

Occurs at a high temperature (approx. 800 degrees C) primary mineral in granite pegmatites.

IMA Status:

Valid Species (Pre-IMA) 1925

Locality:

In Brazil, from the Sierra Branca pegmatite, 13 km south of Pedra Lavrada, Picui, Paraiba; in the Enio pegmatite mine, northeast of Galileia, and the Sapucaia pegmatite mine, about 50 Link to MinDat.org Location Data.

Name Origin:

To honor Miguel Arrojado Ribeiro Lisboa (1872-1932), Brazilian geologist.

Synonym:

ICSD 100872

PDF 34-149

Arrojadite Image

Images:

Arrojadite

Comments: Brownish to clear crystals of arrojadite on matrix.
Location: Big Fish river area, Yukon Territory, Canada. Scale: Picture size 4 mm.
© Thomas Witzke / Abraxas-Verlag

Images:

Arrojadite

Comments: Tabular, diamond shaped golden yellow crystal of arrojadite.
Location: Rapid Creek, Yukon, Canada. Scale: Crystal to 5mm..
© Tom Loomis / Dakota Matrix

Arrojadite Crystallography

Axial Ratios:

a:b:c =1.6444:1:2.4612

Cell Dimensions:

a = 16.537, b = 10.056, c = 24.75, Z = 4; beta = 105.65° V = 3,963.24 Den(Calc)= 3.60

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/c

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

By Intensity(I/I_o): 3.042(1), 2.714(0.85), 3.222(0.45),

Crystal Structure:

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Moore P B , Araki T , Merlino S , Mellini M , Zanazzi P F , American Mineralogist , 66 (1981) p.1034-1049, The arrojadite-dickinsonite series, KNa4Ca(Fe,Mn)14Al(OH)2(PO4)12:, Crystal structure and crystal chemistry, sample NM

View Additional jPOWD Structure files for Arrojadite
[1]

Physical Properties of Arrojadite

Cleavage:

[001] Distinct

Color:

Olive green, Clove brown, Yellow.

Density:

3.56

Diaphaniety:

Translucent

Fracture:

Conchoidal - Uneven - Uneven fracture producing small, conchoidal fragments.

Hardness:

5 - Apatite

Luster:

Vitreous - Greasy

Streak:

green gray

Optical Properties of Arrojadite

Gladstone-Dale:

CI meas= 0.006 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.017 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.186,KPDmeas= 0.1881,KC= 0.1892

Optical Data:

Biaxial (+), a=1.664, b=1.67, g=1.675, bire=0.0110, 2V(Calc)=84, 2V(Meas)=86.

Calculated Properties of Arrojadite

Electron Density:

r_electron=3.44 gm/cc
note: r_Arrojadite=3.56 gm/cc.

Fermion Index

Fermion Index = 0.0057
Boson Index = 0.9943

Photoelectric:

PE_Arrojadite= 11.79 barns/electron
U=PE_Arrojadite x r_electron= 40.52 barns/cc.

Radioactivity:

GRapi = 25.32 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Arrojadite - barely detectable

Arrojadite Classification

Dana Class:

41.7.2.1 (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen

(41.7)where (A B)m (XO4)4 Zq

(41.7.2)Dana Group

41.7.2.1 Arrojadite KNa4CaMn4Fe10Al(PO4)12(OH,F)2 C 2/c 2/m

41.7.2.2 Dickinsonite KNa4Ca(Mn,Fe)14Al(PO4)12(OH)2 C 2/c 2/m

Strunz Class:

VII/B.20-10 VII - Phosphates, Arsenates and Vanadates

VII/B - Waterfree phosphates with unfamiliar anions F, Cl, O, OH. cations of medium and big size: Mg, Cu, Zn, and Ca, Na, K, Ba, Pb

VII/B.20 - Arrojadite - Samuelsonite series

VII/B.20-10 Arrojadite KNa4CaMn4Fe10Al(PO4)12(OH,F)2 C 2/c 2/m

VII/B.20-20 Dickinsonite KNa4Ca(Mn,Fe)14Al(PO4)12(OH)2 C 2/c 2/m

VII/B.20-25 Sigismundite! (Ba,K,Pb)Na3(Ca,Sr)(Fe,Mg,Mn)14Al(OH)2(PO4)12 C 2/c 2/m

VII/B.20-30 Samuelsonite (Ca,Ba)Ca8(Fe,Mn)4Al2(PO4)10(OH)2 C 2/m 2/m

VII/B.20-40 Nabiasite! BaMn9[(V,As)O4]6(OH)2 P a3 2/m 3

Other Arrojadite Information

References:

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

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Arrojadite

KNa4CaMn++4Fe++10Al(PO4)12(OH,F)2
Dana No: 41.7.2.1 Strunz No: VII/B.20-10
Locality:

Notes: