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Oligoclase

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Big Photo

Chihuahua, Mexico
© Rob Lavinsky

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Formula:
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
Colour:Colourless, white, very ...Hardness:6 - 6½
Member of:Feldspar Group
A variety of Albite

A plagioclase feldspar with an albite : anorthite molar ratio ranging from 90 : 10 to 70 : 30.

Originally described from Danvikstull, Stockholm, Södermanland, Sweden.

Visit gemdat.org for gemological information about Oligoclase. Currently in public beta-test.

Classification of Oligoclase

Strunz 8th edition ID:8/J.07-30
Nickel-Strunz 10th (pending) edition ID:9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
A : Tektosilicates without additional non-tetrahedral anions
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Physical Properties of Oligoclase

Lustre:Vitreous, Sub-Vitreous
Diaphaneity (Transparency):Transparent, Translucent
Colour:Colourless, white, very pale yellow
Comment:may be green due to inclusions
Streak:White
Hardness (Mohs):6 - 6½
Tenacity:Brittle
Cleavage:Perfect
{001} perfect, {010} good, {110} poor
Fracture:Irregular/Uneven, Sub-Conchoidal, Step-Like
Comment:The angles between the good and perfect cleavages are usually 93-94 degrees
Density (measured):2.63 - 2.66 g/cm3
Density (calculated):2.65 g/cm3

Chemical Properties of Oligoclase

Formula:
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
Essential elements:Al, Na, O, Si
All elements listed in formula:Al, Ca, Na, O, Si
Analytical Data:Refractive Index is related to chemical composition and increase with CaAl substitution: alpha 1.533-1.544, beta 1.537-1.548, gamma 1.542-1.552; birefringence 0.008-0.009
Relationship of Oligoclase to other Species
Member of:Feldspar Group
Other Members of Group:

- + 
Albite
NaAlSi
 
3
O
 
8
Andesine
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
Anorthite
CaAl
 
2
Si
 
2
O
 
8
Anorthoclase
(Na,K)AlSi
 
3
O
 
8
Banalsite
BaNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
Buddingtonite
(NH
 
4
)AlSi
 
3
O
 
8
Bytownite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
Celsian
BaAl
 
2
Si
 
2
O
 
8
Dmisteinbergite
CaAl
 
2
Si
 
2
O
 
8
Hyalophane
(K,Ba)[Al(Si,Al)Si
 
2
O
 
8
]
Labradorite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
Microcline
KAlSi
 
3
O
 
8
Orthoclase
KAlSi
 
3
O
 
8
Paracelsian
BaAl
 
2
Si
 
2
O
 
8
Reedmergnerite
Na[BSi
 
3
O
 
8
]
Sanidine
KAlSi
 
3
O
 
8
Slawsonite
(Sr,Ca)Al
 
2
Si
 
2
O
 
8
Stronalsite
SrNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
Svyatoslavite
CaAl
 
2
Si
 
2
O
 
8
Related Minerals - Nickel-Strunz Grouping):

- + 
9.FA.05Kaliophilite
KAlSiO
 
4
9.FA.05Kalsilite
KAlSiO
 
4
9.FA.05Nepheline
(Na,K)AlSiO
 
4
9.FA.05Panunzite
(K,Na)AlSiO
 
4
9.FA.05Trikalsilite
(K,Na)AlSiO
 
4
9.FA.05Yoshiokaite
(Ca,Na)[Al(Al,Si)O
 
4
]
9.FA.05Megakalsilite
KAlSiO
 
4
9.FA.10Malinkoite
NaBSiO
 
4
9.FA.15Virgilite
LiAlSi
 
2
O
 
6
9.FA.25Lisitsynite
KBSi
 
2
O
 
6
9.FA.30Adularia
KAlSi
 
3
O
 
8
9.FA.30Anorthoclase
(Na,K)AlSi
 
3
O
 
8
9.FA.30Buddingtonite
(NH
 
4
)AlSi
 
3
O
 
8
9.FA.30Celsian
BaAl
 
2
Si
 
2
O
 
8
9.FA.30Hyalophane
(K,Ba)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.30Microcline
KAlSi
 
3
O
 
8
9.FA.30Orthoclase
KAlSi
 
3
O
 
8
9.FA.30Sanidine
KAlSi
 
3
O
 
8
9.FA.30Rubicline
(Rb,K)AlSi
 
3
O
 
8
9.FA.30Monalbite
NaAlSi
 
3
O
 
8
9.FA.35Albite
NaAlSi
 
3
O
 
8
9.FA.35Andesine
(Na,Ca)[Al(Si,Al)Si
 
2
O
 
8
]
9.FA.35Anorthite
CaAl
 
2
Si
 
2
O
 
8
9.FA.35Bytownite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
9.FA.35Labradorite
(Ca,Na)[Al(Al,Si)Si
 
2
O
 
8
]
9.FA.35Reedmergnerite
Na[BSi
 
3
O
 
8
]
9.FA.40Paracelsian
BaAl
 
2
Si
 
2
O
 
8
9.FA.45Svyatoslavite
CaAl
 
2
Si
 
2
O
 
8
9.FA.45Kumdykolite
NaAlSi
 
3
O
 
8
9.FA.50Slawsonite
(Sr,Ca)Al
 
2
Si
 
2
O
 
8
9.FA.55Lisetite
CaNa
 
2
Al
 
4
Si
 
4
O
 
16
9.FA.60Banalsite
BaNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
9.FA.60Stronalsite
SrNa
 
2
[Al
 
2
Si
 
2
O
 
8
]
 
2
9.FA.65Danburite
CaB
 
2
Si
 
2
O
 
8
9.FA.65Maleevite
BaB
 
2
Si
 
2
O
 
8
9.FA.65Pekovite
SrB
 
2
Si
 
2
O
 
8
9.FA.70Lingunite
(Na,Ca)AlSi
 
3
O
 
8
9.FA.75Kokchetavite
KAlSi
 
3
O
 
8
Other Names for Oligoclase
Synonyms:
Adventurine OligoclaseAmansiteAmanticeAmantiteAmausite
LluviaOligoalbiteOligoclasiteSoda-Spodumene (of Dana)Sodium Spodumene
Tschermakite (of Kobell)
Other Languages:
German:Amansit
Amantit
Amausit
Luotolit
Oligoklas
Oligoklasit
Simplified Chinese:奥长石
更长石
Spanish:Amansita
Amantita
Amausita
Oligoclasita
Varieties:
Lazur-FeldspathOligoclase-Albite
Other Information
Fluorescence in UV light:Not usually fluorescent in SW UV; may be faint red to faint white.
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 Oligoclase
Reference List:

- + 
American Mineralogist (1968): 53: 1709-1723.



Zeitschrift für Kristallographie (1971): 133: 43.


Internet Links for Oligoclase
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