polylithionite - KLi2AlSi4O10F2

Polylithionite is a phyllosilicate mineral, member of the Mica group. The name was introduced by Lorenzen (1884) and comes from the Greek "Poly" for "many or much" and Lithium, in allusion to its composition with a high Lithium. It was fist discovered in a lithium-rich syenite pegmatites at Kangerdluarssuk in Greenland. Polylithionite, like other micas, has a layered structure of lithium aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage. Polylithionite is a common mineral in irregular segregation and veinlets, as late stage and metasomatic replacement mineral, in syenite pegmatites and in alkalic or agpaitic rocks (Lovozero, Ilìmaussaq, Mont Saint-Hilaire etc).

Optical Properties:
Form: Occurs as tabular-micaceous crystals, also scaly, fine grained.
Relief: Low.
Color: Colorless.
Pleochroism: None to weak.
Cleavage: (001) perfect.
Interference colors: Medium-low (from gray to yellow-orange).

polylithionite.jpg

Micaceous crystals of polylithionite from Ilimaussaq complex, Narsaq.



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
polylithionite(1).jpg

Polylithionite crystals (colorless) in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 10x (Field of view = 2mm)
polylithionite(2).jpg

Polylithionite crystals (yellow-orange) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 10x (Field of view = 2mm)
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Polylithionite crystals (colorless), eudyalite (high relief) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 10x (Field of view = 2mm)
polylithionite(4).jpg

Polylithionite crystals (yellow), eudyalite (gray) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 10x (Field of view = 2mm)
polylithionite(5).jpg

Polylithionite crystals (colorless), aegirine (green) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 10x (Field of view = 2mm)
polylithionite(6).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 10x (Field of view = 2mm)
polylithionite(12).jpg

Polylithionite crystals (gray), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(9).jpg

Polylithionite crystals (colorless), aegirine (green) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 20x (Field of view = 1mm)
polylithionite(10).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(15).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(13).jpg

Polylithionite crystals (colorless), aegirine (green) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 20x (Field of view = 1mm)
polylithionite(14).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(18).jpg

Polylithionite crystals (yellow-orange), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(16).jpg

Polylithionite crystals (colorless), aegirine (green) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 20x (Field of view = 1mm)
polylithionite(17).jpg

Polylithionite crystals (yellow-orange), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(25).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(26).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(27).jpg

Polylithionite crystals (yellow), aegirine and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(20).jpg

Polylithionite crystals (colorless), eudyalite (high relief) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. PPL image, 20x (Field of view = 1mm)
polylithionite(21).jpg

Polylithionite crystals (yellow), eudyalite (gray) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)
polylithionite(22).jpg

Polylithionite crystals (yellow), eudyalite (gray) and feldspar in a agpaitic syenite. Ilimaussaq complex, Greenland. XPL image, 20x (Field of view = 1mm)