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Prehnite

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Jeffrey Mine (Jeffrey Quarry), Asbestos, Shipton Township, Richmond Co., Québec, Canada
© 2001 John H. Betts

Show Prehnite Photos (713)
Formula:
Ca
 
2
Al
 
2
Si
 
3
O
 
12
(OH)
System:OrthorhombicColour:Colourless to gray to ...
Lustre:Vitreous, PearlyHardness:6 - 6½
Name:Named after the Dutch Colonel, H. Von Prehn (1733-1785).
This page provides mineralogical data about Prehnite.

Classification of Prehnite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/G.07-30
Nickel-Strunz 10th (pending) edition ID:9.DP.20

9 : SILICATES (Germanates)
D : Inosilicates
P : Transitional ino-phyllosilicate structures
Dana 8th edition ID:72.1.3.1

72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
Hey's CIM Ref.:16.9.10

16 : Silicates Containing Aluminum and other Metals
9 : Aluminosilicates of Ca
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Type Occurrence of Prehnite

Type Locality:Karoo dolerites, Craddock District, Eastern Cape Province, South Africa
Year of Discovery:1788

Occurrences of Prehnite

Geological Setting:A secondary mineral in mafic volcanic rocks, low grade metamorphic mineral.

Physical Properties of Prehnite

Lustre:Vitreous, Pearly
Diaphaneity (Transparency):Semitransparent, Translucent
Comment:Pearly on cleavage {001}
Colour:Colourless to gray to yellow, yellow-green or white
Streak:White
Hardness (Mohs):6 - 6½
Tenacity:Brittle
Cleavage:Distinct/Good
Good on {001}, poor on {110}
Fracture:Irregular/Uneven
Density (measured):2.8 - 2.95 g/cm3
Density (calculated):2.9 g/cm3

Crystallography of Prehnite

Crystal System:Orthorhombic
Class (H-M):mm2 - Pyramidal
Cell Parameters:a = 4.646(2) Å, b = 5.491(3) Å, c = 18.52(3) Å
Ratio:a:b:c = 0.846 : 1 : 3.373
Unit Cell Volume:V 472.47 ų (Calculated from Unit Cell)
Z:2
Morphology:Uncommon crystals, aggregates are fanlike, reniform, globular, stalagtitic, granular, compact.
Twinning:Fine lamellar
X-Ray Powder Diffraction:
Image Loading

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.

Optical Data of Prehnite

Type:Biaxial (+)
RI values: nα = 1.611 - 1.632 nβ = 1.615 - 1.642 nγ = 1.632 - 1.665
2V:Measured: 64° to 70°, Calculated: 58° to 68°
Maximum Birefringence:δ = 0.021 - 0.033

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

Chemical Properties of Prehnite

Formula:
Ca
 
2
Al
 
2
Si
 
3
O
 
12
(OH)
Essential elements:Al, Ca, H, O, Si
All elements listed in formula:Al, Ca, H, O, Si
Common Impurities:Ti,Fe,Mg,Na,K,H2O

Relationship of Prehnite to other Species

Related Minerals - Nickel-Strunz Grouping):
9.DP.05Meliphanite
(Ca,Na)
 
2
(Be,Al)[Si
 
2
O
 
6
(OH,F)]
9.DP.15Leucosphenite
BaNa
 
4
Ti
 
2
B
 
2
Si
 
10
O
 
30
9.DP.25Amstallite
CaAl(Si,Al)
 
4
O
 
8
(OH)
 
4
·(H
 
2
O,Cl)
9.DP.30Kvanefjeldite
Na
 
4
(Ca,Mn)(Si
 
3
O
 
7
)
 
2
(OH)
 
2
9.DP.35Lemoynite
(Na,K)
 
2
CaZr
 
2
Si
 
10
O
 
26
·5H
 
2
O
9.DP.35Natrolemoynite
Na
 
4
Zr
 
2
Si
 
10
O
 
26
•
 
9
H
 
2
O
9.DP.40Altisite
Na
 
3
K
 
6
Ti
 
2
Al
 
2
Si
 
8
O
 
26
Cl
 
3
Related Minerals - Hey's Index Grouping:
16.9.1Gehlenite
Ca
 
2
Al[AlSiO
 
7
]
16.9.2Anorthite
Ca[Al
 
2
Si
 
2
O
 
8
]
16.9.3Yoshiokaite
(Ca,Na)[Al(Al,Si)O
 
4
]
16.9.4Svyatoslavite
Ca[Al
 
2
Si
 
2
O
 
8
]
16.9.5Dmisteinbergite
Ca[Al
 
2
Si
 
2
O
 
8
]
16.9.6Grossular
Ca
 
3
Al
 
2
[SiO
 
4
]
 
3
16.9.7Vuagnatite
CaAl[OH|SiO
 
4
]
16.9.8Zoisite
{Ca
 
2
}{Al
 
3
}[O|OH|SiO
 
4
|Si
 
2
O
 
7
]
16.9.9Clinozoisite
{Ca
 
2
}{Al
 
3
}[O|OH|SiO
 
4
|Si
 
2
O
 
7
]
16.9.11Kamaishilite
Ca
 
2
[(OH)
 
2
|Al
 
2
SiO
 
6
]
16.9.12Bicchulite
Ca
 
2
[(OH)
 
2
|Al
 
2
SiO
 
6
]
16.9.13Margarite
CaAl
 
2
[(OH)
 
2
|Al
 
2
Si
 
2
O
 
10
]
16.9.14Chantalite
CaAl
 
2
[(OH)
 
4
|SiO
 
4
]
16.9.15Cebollite
Ca
 
5
Al
 
2
Si
 
3
O
 
12
(OH)
 
4
 or near
16.9.17Katoite
Ca
 
3
Al
 
2
[(OH)
 
8-6
|(SiO
 
4
)
 
1-1.5
]
16.9.18Lawsonite
CaAl
 
2
[(OH)
 
2
|Si
 
2
O
 
7
] · H
 
2
O
16.9.19Parthéite
CaAl
 
2
Si
 
2
O
 
8
·2H
 
2
O
16.9.20Wairakite
Ca[Al
 
2
Si
 
4
O
 
12
] · 2H
 
2
O
16.9.21Vertumnite
Ca
 
4
Al
 
4
Si
 
4
O
 
6
(OH)
 
24
·3H
 
2
O
16.9.22Scolecite
Ca[Al
 
2
Si
 
3
O
 
10
] · 3H
 
2
O
16.9.23Laumontite
CaAl
 
2
Si
 
4
O
 
12
·4H
 
2
O
16.9.24Yugawaralite
CaAl
 
2
Si
 
6
O
 
16
·4H
 
2
O
16.9.25Gismondine-Ca
CaAl
 
2
Si
 
2
O
 
8
·4H
 
2
O
16.9.26Epistilbite
CaAl
 
2
Si
 
6
O
 
16
·5H
 
2
O
16.9.27Goosecreekite
Ca[Al
 
2
Si
 
6
O
 
16
] · 5H
 
2
O
16.9.28Cowlesite
CaAl
 
2
Si
 
3
O
 
10
·6H
 
2
O
16.9.30Stellerite
Ca[Al
 
2
Si
 
7
O
 
18
] · 7H
 
2
O
16.9.31Strätlingite
Ca
 
2
Al
 
2
SiO
 
7
·8H
 
2
O
16.9.32Amstallite
CaAl(Si,Al)
 
4
O
 
8
(OH)
 
4
·(H
 
2
O,Cl)

Other Names for Prehnite

Synonyms:
Adelite (of de Fourestier)AdiliteAedeliteÆdelite (of Walmstedt)Aedilite
ChiltoniteChrysolite (of Sage)CoupholitePrehnitoid (of Bechi)
French names:
Chrysolite du Cap
German names:
AdilitAedelitAedilitChiltonitCoupholit
EdelitPrehnit
Japanese names:
ぶどう石
Russian names:
Пренит
Spanish names:
AdilitaAedelitaAedilitaChiltonitaCoupholita
EdelitaPrehnita
Swedish names:
Ædelforsit (of Walmstedt)

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 Prehnite

Reference List:European Journal of Mineralogy (1990): 2: 731-734.

Canadian Mineralogist (1987): 25: 707.

Internet Links for Prehnite

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

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