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Keiviite-(Yb)

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Formula:
(Yb,Y)
 
2
Si
 
2
O
 
7
System:MonoclinicColour:Colourless
Lustre:VitreousHardness:4 - 5
Member of:Thortveitite Group
Name:For the type locality, Keivy massif

Classification of Keiviite-(Yb)

IMA status:Approved
Strunz 8th edition ID:8/C.01-30
Nickel-Strunz 10th (pending) edition ID:9.BC.05

9 : SILICATES (Germanates)
B : Sorosilicates
C : Si2O7 groups, without non-tetrahedral anions; cations in octahedral [6] and greater coordination
Dana 8th edition ID:55.2.1a.3

55 : SOROSILICATES Si2O7 Groups,Generally with no Additional Anions
2 : Si2O7 Groups, Generally with no Additional Anions with cations in [6] coordination
Hey's CIM Ref.:14.8.3

14 : Silicates not Containing Aluminum
8 : Silicates of Group III metals other than Al
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Type Occurrence of Keiviite-(Yb)

Type Locality:Ploskaya Mt, Western Keivy Massif, Keivy Mountains, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia
Place of Conservation of Type Material:Fersman Museum
Geological Setting of type material:Microcline bearing pegmatites
Associated Minerals at type locality:
FluoriteBastnäsiteBastnäsiteWulfenite

Physical Properties of Keiviite-(Yb)

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Colourless
Hardness (Mohs):4 - 5
Cleavage:Perfect
perfect on {110}, imperfect on {001}
Density (measured):5.95 g/cm3
Density (calculated):5.99 g/cm3

Crystallography of Keiviite-(Yb)

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:B2/m {B1 1 2/m} {C2/m} {C1 2/m 1}
Cell Parameters:a = 6.840(2) Å, b = 8.916(2) Å, c = 4.745(1) Å
β = 102.11(3)°
Ratio:a:b:c = 0.767 : 1 : 0.532
Unit Cell Volume:V 282.94 ų (Calculated from Unit Cell)
Z:2
Morphology:Elongated platy and prismatic crystals
Twinning:Polysynthetic - common

Optical Data of Keiviite-(Yb)

Type:Biaxial (-)
RI values: nα = 1.723 nβ = 1.758 nγ = 1.768
2V:Measured: 58°
Maximum Birefringence:δ = 0.045

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:r < v strong

Chemical Properties of Keiviite-(Yb)

Formula:
(Yb,Y)
 
2
Si
 
2
O
 
7
Simplified for copy/paste:(Yb,Y)2Si2O7
Essential elements:O, Si, Yb
All elements listed in formula:O, Si, Y, Yb

Relationship of Keiviite-(Yb) to other Species

Series:Forms a series with Keiviite-(Y) (see here)
Member of:Thortveitite Group
Other Members of Group:

- +
Keiviite-(Y)
(Y,Yb)
 
2
[Si
 
2
O
 
7
]
Related Minerals - Nickel-Strunz Grouping):

- +
9.BC.05Gittinsite
CaZrSi
 
2
O
 
7
9.BC.05Keiviite-(Y)
(Y,Yb)
 
2
[Si
 
2
O
 
7
]
9.BC.05Thortveitite
(Sc,Y)
 
2
Si
 
2
O
 
7
9.BC.05Yttrialite-(Y)
(Y,Th)
 
2
Si
 
2
O
 
7
9.BC.10Keldyshite
(Na,H)
 
2
ZrSi
 
2
O
 
7
9.BC.10Khibinskite
K
 
2
ZrSi
 
2
O
 
7
9.BC.10Parakeldyshite
Na
 
2
ZrSi
 
2
O
 
7
9.BC.15Rankinite
Ca
 
3
Si
 
2
O
 
7
9.BC.20Barysilite
Pb
 
8
Mn
2+
 
[Si
 
2
O
 
7
]
 
3
9.BC.25Edgarbaileyite
(Hg-Hg)
 
3
Si
 
2
O
 
7
9.BC.30Kristiansenite
Ca
 
2
ScSn(Si
 
2
O
 
7
)(Si
 
2
O
 
6
OH)
9.BC.35Percleveite-(Ce)
(Ce,La,Nd)
 
2
Si
 
2
O
 
7
Related Minerals - Hey's Index Grouping:

- +
14.8.1Thalénite-(Y)
Y
 
3
(Si
 
3
O
 
10
)(OH)
14.8.2Keiviite-(Y)
(Y,Yb)
 
2
[Si
 
2
O
 
7
]
14.8.4Tombarthite-(Y)
Y
 
4
(Si,H
 
4
)
 
4
O
 
12-x
(OH)
 
4+2x
14.8.5Thortveitite
(Sc,Y)
 
2
Si
 
2
O
 
7
14.8.6Sazhinite-(Ce)
Na
 
3
Ce[Si
 
6
O
 
15
] · 6H
 
2
O
14.8.7Monteregianite-(Y)
(Na,K)
 
6
(Y,Ca)
 
2
Si
 
16
O
 
38
· 10H
 
2
O
14.8.8Iraqite-(La)
K(Ca,Na)
 
2
(La,Ce,Th)[(Si,Al)
 
8
O
 
20
]
14.8.9Ashcroftine-(Y)
K
 
5
Na
 
5
(Y,Ca)
 
12
Si
 
28
O
 
70
(OH)
 
2
(CO
 
3
)
 
8
· 8H
 
2
O
14.8.10Nordite-(La)
(La,Ce)(Sr,Ca)Na
 
2
(Na,Mn)(Zn,Mg)Si
 
6
O
 
17
14.8.11Nordite-(Ce)
(Ce,La)(Sr,Ca)Na
 
2
(Na,Mn)(Zn,Mg)Si
 
6
O
 
17
14.8.12Jervisite
(Na,Ca,Fe
2+
 
)(Sc,Mg,Fe
2+
 
)Si
 
2
O
 
6
14.8.13Cerite-(Ce)
(Ce,Ca)
 
9
(Mg,Fe)(SiO
 
4
)
 
3
(HSiO
 
4
)
 
4
(OH)
 
3
14.8.14Cascandite
Ca(Sc,Fe
3+
 
)(HSi
 
3
O
 
9
)

Other Names for Keiviite-(Yb)

Synonyms:
IMA1982-065Keivyite-(Yb)
Other Languages:
Russian:Кейвиит-(Yb)

Other Information

Fluorescence in UV light:Faint green cathodoluminescence
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 Keiviite-(Yb)

Reference List:

- +
American Mineralogist (1984): 69: 1191.

Internet Links for Keiviite-(Yb)

Search Engines:
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  • External Links:
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  • Look for Keiviite-(Yb) on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Keiviite-(Yb) details from Handbook of Mineralogy (PDF)
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  • Localities for Keiviite-(Yb)

    The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
    (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.
    Norway
     
    • Nordland
      • Tysfjord
    Husdal, T. (2008): The minerals of the pegmatites within the Tysfjord granite, northern Norway. Norsk Bergverksmuseum, skrift 38, 5-28.
    Russia
     
    • Northern Region
      • Murmanskaja Oblast'
        • Kola Peninsula
          • Keivy Mountains
            • Western Keivy Massif
    A.V. Voloshin, Ya.A. Pakhomovskii Minerals and mineralformation evolution in amazonite pegmatites of Kola peninsula, - Leningrad, Nauka, 1986, pp.168.
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