Astrophyllite - K2NaFe2+7Ti2Si8O28(OH)4F

Astrophyllite is one of a large group of silicate minerals which occurs as accessory minerals in alkaline igneous rocks. These minerals are characterized chemically by the presence of large amount of sodium, titanium, zirconium and often manganese, and the almost complete absence of aluminum and magnesium. Astrophyllite was first discovered in 1854 at Laven Island, Norway, and the name is from the Greek "astron" for "star" and "phyllon" for "leaf", in allusion to its habit of starburst-like sprays and micaceous cleavage. It is usually found in fissures and cavities in in alkaline igneous rocks.

Optical properties:
Form: Bladed, acicular or tabular crystals.
Cleavage: Perfect on (001) and poor on (100).
Color: Bronze-yellow to gold-yellow, brown to reddish brown.
Pleochroism: Strong, from deep orange-red to lemon-yellow.
Birefringence: High.

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Stellate aggregates of astrophyllite. Eveslogchorr, Kola, Russia. Image from jewellery


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Stellate aggregates of astrophyllite. Eveslogchorr, Kola, Russia.


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Stellate aggregates of astrophyllite. Eveslogchorr, Kola, Russia. Image from Royal Ontario Museum (Toronto).




Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc


Photo
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange) and aegirine (green) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (high interference colors) and aegirine crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
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Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
astrophyllite(51).jpg

Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
astrophyllite(52).jpg

Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
astrophyllite(53).jpg

Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
astrophyllite(81).jpg

Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)
astrophyllite(83).jpg

Astrophyllite (brown-orange), aegirine (green) and eudyalite (pink) crystals in a syenite from Eveslogchorr, Kola, Russia. PPL image, 2x (Field of view = 7mm)