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Iwashiroite-(Y)

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Suishoyama pegmatite (Suishouyama; Suisyoyama; Suishyoyama), Iizaka (Iisaka) Village, Kawamata, Fukushima Prefecture, Tohoku Region, Honshu Island, Japan

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Formula:
Y(Ta,Nb)O
 
4
System:MonoclinicColour:Dark red-brown, amber ...
Hardness:6
Name:Iwashiro was an old name for the district, and is still the name of a neighboring town.


Only one specimen found, in reddish feldspar in pegmatite.
Zoned (U-rich parts are metamict). Also known as a synthetic compound (M'-type YTaO4; Wolten, 1967).

See also formanite-(Y) and yttrotantalite-(Y).

Formanite group

Classification of Iwashiroite-(Y)

IMA status:Approved 2003
Strunz 8th edition ID:4/D.24-80
Nickel-Strunz 10th (pending) edition ID:7.GA.10

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
G : Molybdates, Wolframates and Niobates
A : Without additional anions or H2O
Dana 7th edition ID:8.1.2.4
mindat.org URL:http://www.mindat.org/min-25650.html
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Type Occurrence of Iwashiroite-(Y)

Type Locality:Suishoyama pegmatite (Suishouyama; Suisyoyama; Suishyoyama), Iizaka (Iisaka) Village, Kawamata, Fukushima Prefecture, Tohoku Region, Honshu Island, Japan
General Appearance of Type Material:Aggregate of small euhedral platy crystals
Geological Setting of type material:Yttrium-rich granite pegmatite.
Associated Minerals at type locality:
QuartzMicroclineAnnite

Physical Properties of Iwashiroite-(Y)

Lustre:Sub-Adamantine, Vitreous
Diaphaneity (Transparency):Translucent
Colour:Dark red-brown, amber brown to brown
Streak:Pale brown
Hardness (Mohs):6
Cleavage:Distinct/Good
on {010}, poor on {001}
Density (calculated):7.1 g/cm3

Crystallography of Iwashiroite-(Y)

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Cell Parameters:a = 5.262Å, b = 5.451Å, c = 5.11Å
β = 95.12°
Ratio:a:b:c = 0.965 : 1 : 0.937
Unit Cell Volume:V 146 ų
Z:2
Comment:M'-type YTaO4 modification.
X-Ray Powder Diffraction:
d-spacingIntensity
3.13 (100)
2.95 (94)
2.73 (26)
1.890 (29)
1.862 (29)
Comments:Format: d/Å (I/%) (hkl)
From type description

Chemical Properties of Iwashiroite-(Y)

Formula:
Y(Ta,Nb)O
 
4
All elements listed in formula:Nb, O, Ta, Y
Analytical Data:Results from electron microprobe analysis
Empirical formula calculated on the basis of four oxide ions per formula unit
Y2O3 (29.10)
Ce2O3 (0.10)
Nd2O3 (0.10)
Sm2O3 (0.36)
Gd2O3 (1.06)
Tb2O3 (0.25)
Dy2O3 (2.38)
Ho2O3 (0.56)
Er2O3 (2.09)
Tm2O3 (0.37)
Yb2O3 (3.33)
Lu2O3 (0.85)
ThO2 (0.02)
UO2 (0.15)
CaO (0.17)
Ta2O5 (40.64)
Nb2O5 (16.66)
TiO2 (0.41)

sum 98.60 wt.-%
Empirical Formula:
(Y
 
0.81
Yb
 
0.05
Dy
 
0.04
 Er
 
0.03
Gd
 
0.02
Lu
 
0.01
Ho
 
0.01
Sm
 
0.01
Ca
 
0.01
Tm
 
0.01
)
 
Σ1.00
(Ta
 
0.58
Nb
 
0.39
Ti
 
0.02
)
 
Σ0.99
O
 
4
Common Impurities:REE,Ti,U

Relationship of Iwashiroite-(Y) to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
7.GA.05Fergusonite-(Ce)
(Ce,La,Nd)NbO
 
4
7.GA.05Fergusonite-(Nd)
(Nd,Ce)(Nb,Ti)O
 
4
7.GA.05Fergusonite-(Y)
YNbO
 
4
7.GA.05Powellite
Ca(MoO
 
4
)
7.GA.05Scheelite
Ca(WO
 
4
)
7.GA.05Stolzite
Pb(WO
 
4
)
7.GA.05Wulfenite
Pb(MoO
 
4
)
7.GA.10Formanite-(Y)
YTaO
 
4
7.GA.15Paraniite-(Y)
Ca
 
2
Y(AsO
 
4
)(WO
 
4
)
 
2

Other Names for Iwashiroite-(Y)

Synonyms:
IMA2003-053
Other Languages:
German:Iwashiroit-(Y)
Japanese:岩代石

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Iwashiroite-(Y)

Reference List:

- +
Wolten, G.M. (1967): The structure of the M'-phase of YTaO4, a third fergusonite polymorph. Acta Crystallogr., 23, 939-944.

Miyawaki et al. (2003) Kobutsu-Gakkai Koen-Yoshi, 212.

Hori, H., Kobayashi, T., Miyawaki, R., Matsubara, S., Yokoyama, K., Shimizu, M. (2006): Iwashiroite-(Y), YTaO4, a new mineral from Suishoyama, Kawamata Town, Fukushima Prefecture, Japan. Journal of Mineralogical and Petrological Sciences, 101, 170-177.

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    • Localities for Iwashiroite-(Y)

    Hide Locality List
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Japan
     
    • Honshu Island
      • Tohoku Region
        • Fukushima Prefecture
          • Kawamata
            • Iizaka (Iisaka) Village
    		Hori, H., Kobayashi, T., Miyawaki, R., Matsubara, S., Yokoyama, K., Shimizu, M. (2006): Iwashiroite-(Y), YTaO4, a new mineral from Suishoyama, Kawamata Town, Fukushima Prefecture, Japan. Journal of Mineralogical and Petrological Sciences, 101, 170-177.
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