THE MINERAL POLYLITHIONITE

Chemistry: KLi2AlSi4O10F2, Potassium Lithium Aluminum Silicate Fluoride.
Class: Silicates
Subclass: Phyllosilicates
Group: Micas
Division: True Micas
Uses: Only as mineral specimens.
Specimens

Polylithionite, which is named from the Greek for having much lithium, is not a well know mineral. Yet it is an attractive mineral that is available on the mineral markets. The best specimens arguably come from the famous quarry at Mont Saint-Hilaire, Quebec, Canada. Specimens there are found mostly in the altered and unaltered pegmatites with other rare minerals. Polylithionite is found at other alkaline rich pegmatitic deposits such as the Ilimaussaq alkaline complex in Greenland and at Langesundsfjord, Norway. Polylithionite is fluorecent lemon yellow and this makes distinguishing it from most other micas rather easy. Its habit to form rosettes is distinctive as well. Any yellow to silvery white, fluorescent mica like crystals attached to specimens of other Mont Saint-Hilaire specimens are probably polylithionite.

Polylithionite is certainly not one of the more well know mica minerals. It is a true mica closely related to other lithium rich micas; lepidolite and tainiolite. 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's rarity, associations with other rare minerals, attractive color and fluorescent color and crystal habit make it an ideal collection mineral.

PHYSICAL CHARACTERISTICS:

Color is colorless, white, bluish, greenish, yellow, brown, pink, silvery to pearly white.
Luster is pearly to waxy.
Transparency crystals are transparent to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include pseudohexagonal tabular to platy crystals forming "books" and rosettes.
Cleavage is perfect in one direction producing thin sheets or flakes.
Fracture is not readily observed due to cleavage but is uneven.
Hardness is 2 - 3.
Specific Gravity is approximately 2.6 - 2.8 (average)
Streak is white.
Other Characteristics: Specimens are fluorecent lemon yellow under shortwave UV light.
Associated Minerals are many and include catapleiite, ilmenite, behoite, titanite, aragonite, eudialyte, leucosphenite, fluorite, willemite, apophyllite, rhodochrosite, steacyite, leifite, sodalite, pyrochlore, calcite, sugilite, microcline, axinite, manganbabingtonite, galena, ancylite, natrolite, serandite, hilairite, sheldrickite and calcioancylite.
Notable Occurrences include the type locality of Kangerdluarsuk, Ilimaussaq alkaline complex, Greenland as well as Langesundsfjord, Norway; Varutrask, Sweden; Washington Pass, Okanogan County, Washington; Landsman Camp, Graham County, Arizona and Point of Rocks, New Mexico, USA; Dara-i-Poiz Massif, Tadzhikistan and of course Mont Saint-Hilaire, Quebec, Canada.
Best Field Indicators are crystal habit, fluorescence, color, cleavage, locality and associations.