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Phenakite

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Mogok, Sagaing District, Mandalay Division, Burma (Myanmar)
© Sarah Sudcowsky

Show Phenakite Photos (126)
Formula:
Be
 
2
[SiO
 
4
]
System:TrigonalColour:Colourless, white, ...
Hardness:7½ - 8
Name:Named in 1833 by Nordenskiold from the Greek for "deceiver" in allusion to its being mistaken for quartz.


Phenakite Group.

Classification of Phenakite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/A.01-10
Nickel-Strunz 10th (pending) edition ID:9.AA.05

9 : SILICATES (Germanates)
A : Nesosilicates
A : Nesosilicates without additional anions; cations in tetrahedral [4] coordination
Dana 7th edition ID:51.1.1.1
Dana 8th edition ID:51.1.1.1

51 : NESOSILICATES Insular SiO4 Groups Only
1 : Insular SiO4 Groups Only with cations in [4] coordination
Hey's CIM Ref.:14.3.1

14 : Silicates not Containing Aluminum
3 : Silicates of Be
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Type Occurrence of Phenakite

Type Locality:Emerald mines (Izumrudnye Kopi; Malyshevskoe deposit), Tokovaya river (Tokovaia river), Malyshevo, Ekaterinburg (Sverdlovsk), Ekaterinburgskaya (Sverdlovskaya) Oblast', Middle Urals, Urals Region, Russia
Geological Setting of type material:In schist

Occurrences of Phenakite

Geological Setting:In granite pegmatites and schists

Physical Properties of Phenakite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Colourless, white, yellow, pale rose
Hardness (Mohs):7½ - 8
Tenacity:Brittle
Cleavage:Distinct/Good
Distinct {11_20} and imperfect {10_11}
Fracture:Conchoidal
Density (measured):2.96 - 3 g/cm3
Density (calculated):2.96 g/cm3

Crystallography of Phenakite

Crystal System:Trigonal
Class (H-M):3 - Rhombohedral
Space Group:R3
Cell Parameters:a = 12.438Å, c = 8.231Å
Ratio:a:c = 1 : 0.662
Unit Cell Volume:V 1,102.77 ų (Calculated from Unit Cell)
Z:18
Morphology:Flattened rhombohedra, often highly modified. Dominant forms {11_20}, {10_10}, {10_11}, {12_32}, {11_23}, {2_1_13}, {01_12}. Tabular to prismatic, less commonly long prismatic to acicular to 20 cm. In columnar aggregates, as spherulites, and granular.
Twinning:Penetration twins on {_1010}, twin axis [0001]
Crystal Atlas:
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Phenakite no.34 - Goldschmidt (1913-1926)
Phenakite no.65 - Goldschmidt (1913-1926)

About Crystal Atlas

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction:
d-spacingIntensity
3.12 (100)
3.66(80)
2.52(70)
2.36(70)
2.19(60)
2.08(50)
6.24(40)

Optical Data of Phenakite

Type:Uniaxial (+)
RI values: nω = 1.650 - 1.656 nε = 1.667 - 1.670
Maximum Birefringence:δ = 0.017

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate

Chemical Properties of Phenakite

Formula:
Be
 
2
[SiO
 
4
]
Essential elements:Be, O, Si
All elements listed in formula:Be, O, Si
Analytical Data:From Ural Mountains, Russia
Insoluble in acids
SiO2 (52.92)
Al2O3 (trace)
BeO (45.82)
MgO (0.13)
CaO (0.20)
Na2O (0.63)
K2O (0.26)
LOI (0.21)

Relationship of Phenakite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
9.AA.05Eucryptite
LiAl[SiO
 
4
]
9.AA.05Willemite
Zn
 
2
[SiO
 
4
]
9.AA.10Liberite
Li
 
2
Be[SiO
 
4
]
Related Minerals - Hey's Index Grouping:

- +
14.3.2Bertrandite
Be
 
4
[(OH)
 
2
|Si
 
2
O
 
7
]
14.3.3Beryllite
Be
 
3
[(OH)
 
2
|SiO
 
4
] · H
 
2
O
14.3.4Liberite
Li
 
2
Be[SiO
 
4
]
14.3.5Chkalovite
Na
 
2
BeSi
 
2
O
 
6
14.3.6Eudidymite
Na
 
2
Be
 
2
Si
 
6
O
 
15
·H
 
2
O
14.3.7Epididymite
Na
 
2
Be
 
2
Si
 
6
O
 
15
·H
 
2
O
14.3.8Gugiaite
Ca
 
2
Be[Si
 
2
O
 
7
]
14.3.9Jeffreyite
(Ca,Na)
 
2
(Be,Al)[Si
 
2
O
 
6
(O,OH)]
14.3.10Semenovite-(Ce)
(Na,Ca)
 
9
Fe
2+
 
(Ce,La)
 
2
[(Si,Be)
 
5
(O,OH,F)
 
12
]
 
4
14.3.11Barylite
BaBe
 
2
[Si
 
2
O
 
7
]
14.3.12Hingganite-(Ce)
Ce
 
2
□Be
 
2
Si
 
2
O
 
8
(OH)
 
2
14.3.13Hingganite-(Yb)
(Yb,Y)Be[OH|SiO
 
4
]
14.3.14Hingganite-(Y)
(Y,Yb,Er)Be[OH|SiO
 
4
]
14.3.15Minasgeraisite-(Y)
Y
 
2
CaBe
 
2
[O|SiO
 
4
]
 
2
14.3.16Sørensenite
Na
 
4
SnBe
 
2
Si
 
6
O
 
16
(OH)
 
4
14.3.17Trimerite
CaMn
2+
2
Be
 
3
[SiO
 
4
]
 
3
14.3.18Chiavennite
CaMnBe
 
2
Si
 
5
O
 
13
(OH)
 
2
·2H
 
2
O
14.3.19Tvedalite
(Ca,Mn)
 
4
Be
 
3
Si
 
6
O
 
17
(OH)
 
4
·3H
 
2
O
14.3.20Harstigite
Ca
 
6
(Mn,Mg)Be
 
4
Si
 
6
(O,OH)
 
24
14.3.21Sverigeite
NaMnMgSnBe
 
2
Si
 
3
O
 
12
(OH)
14.3.22Joesmithite
[(Ca,Pb)][(Ca,Pb)
 
2
][(Mg,Fe
2+
 
)
 
5
][(OH)
 
2
|BeSi
 
7
O
 
22
]
14.3.23Gadolinite-(Y)
Y
 
2
Fe
2+
 
Be
 
2
[O|SiO
 
4
]
 
2
14.3.24Gadolinite-(Ce)
(Ce,La,Nd,Y)
 
2
Fe
2+
 
Be
 
2
[O|SiO
 
4
]
 
2
14.3.25Calciogadolinite
(Y,Ca)
 
2
(Fe,Fe)Be
 
2
Si
 
2
(O,OH)
 
10
Related Minerals - Dana Grouping):

- +
51.1.1.2Willemite
Zn
 
2
[SiO
 
4
]
51.1.1.3Eucryptite
LiAl[SiO
 
4
]

Other Names for Phenakite

Synonyms:
Phenacite
Other Languages:
German:Phenacit
Phenakit
Russian:Фенакит

Other Information

Thermal Behaviour:Fusibility 7
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 Phenakite

Reference List:Schaller, Waldemar Theodore (1911), Krystallographische Notizen ueber Albit, Phenakit, und Neptunit: Zeitschr. Kristallographie, Band 48: 550-558; …USGS Bull. 490: 53-56 (1911).

Soviet Physics – Crystallography: 16: 1021-1025.

American Mineralogist (1978): 63: 664.

Internet Links for Phenakite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Phenakite in the Natural History Museum (London) online catalogue
  • Phenakite details from Handbook of Mineralogy (PDF)
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    Localities for Phenakite

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