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Phenakite

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Formula:
Be2SiO4
System:
Trigonal
Colour:
Colourless, white, ...
Hardness:
7½ - 8
Name:
Named in 1833 by Nordenskiold from the Greek for "deceiver" in allusion to its being mistaken for quartz.

Classification of Phenakite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.AA.05

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

51 : NESOSILICATES Insular SiO4 Groups Only
1 : Insular SiO4 Groups Only with cations in [4] coordination
14.3.1

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

Geological Setting of Type Material:
In schist

Occurrences of Phenakite

Geological Setting:
In granite pegmatites and schists

Physical Properties of Phenakite

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:
2.96 - 3 g/cm3 (Measured)    2.96 g/cm3 (Calculated)

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]

Crystallographic forms of Phenakite

Crystal Atlas:
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Phenakite no.34 - Goldschmidt (1913-1926)
Phenakite no.65 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
3.12 (100)
3.66(80)
2.52(70)
2.36(70)
2.19(60)
2.08(50)
6.24(40)
3.60 (30)

Optical Data of Phenakite

Type:
Uniaxial (+)
RI values:
nω = 1.650 - 1.656 nε = 1.667 - 1.670
Max Birefringence:
δ = 0.017
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate

Chemical Properties of Phenakite

Formula:
Be2SiO4
Essential elements:
All elements listed in formula:
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

Structurally related to group(s):
14.3.2BertranditeBe4(Si2O7)(OH)2
14.3.3BerylliteBe3(SiO4)(OH)2 · H2O
14.3.4LiberiteLi2BeSiO4
14.3.5ChkaloviteNa2BeSi2O6
14.3.6EudidymiteNa2Be2Si6O15 · H2O
14.3.7EpididymiteNa2Be2Si6O15 · H2O
14.3.8GugiaiteCa2Be(Si2O7)
14.3.9Jeffreyite(Ca,Na)2(Be,Al)(Si2O7,HSi2O7)
14.3.10Semenovite-(Ce)Na8Ca2FeBe6Ce2Si14O40(OH)4F4
14.3.11BaryliteBe2Ba(Si2O7)
14.3.12Hingganite-(Ce)(Ce,REE)2(□,Fe2+)Be2[SiO4]2(OH)2
14.3.13Hingganite-(Yb)(Yb,Y,REE)2□Be2[SiO4]2(OH)2
14.3.14Hingganite-(Y)(Y,REE,Ca)2(□,Fe2+)Be2[SiO4]2(OH)2
14.3.15Minasgeraisite-(Y)CaBe2Y2Si2O10
14.3.16SørenseniteNa4SnBe2Si6O16(OH)4
14.3.17TrimeriteCaMn22+Be3(SiO4)3
14.3.18ChiavenniteCaMnBe2Si5O13(OH)2 · 2H2O
14.3.19Tvedalite(Ca,Mn)4Be3Si6O17(OH)4 · 3H2O
14.3.20HarstigiteCa6(Mn,Mg)Be4Si6(O,OH)24
14.3.21SverigeiteNaMnMgSnBe2(SiO4)3(OH)
14.3.22Joesmithite{Pb}{Ca2}{Mg3Fe23+}(Be2Si6O22)(OH)2
14.3.23Gadolinite-(Y)Y2Fe2+Be2Si2O10
14.3.24Gadolinite-(Ce)(Ce,La,Nd,Y)2Fe2+Be2Si2O10
14.3.25Calciogadolinite-(Y)(YCa)2Fe3+Be2[SiO4]2O2

Other Names for Phenakite

Name in Other Languages:
Simplified Chinese:硅铍石
似晶石
Traditional Chinese:矽鈹石
似晶石

Other Information

Thermal Behaviour:
Fusibility 7
Health Risks:
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

Specimens:
The following Phenakite specimens are currently listed for sale on minfind.com.

Localities for Phenakite

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.
Mineral and/or Locality  
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