Petalite: Difference between revisions

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			{{Infobox mineral
	{{In\\
			\| name = Petalite
		⚫	\| category = ]
		⚫	\| boxwidth =
			\| boxbgcolor =
			\| image = Petalite.jpg
			\| imagesize =
			\| caption = Petalite from Minas Gerais State, Brazil (size: 3x4 cm)
			\| formula = LiAlSi<sub>4</sub>O<sub>10</sub>
			\| molweight =
			\| strunz = 09.EF.05
			\| symmetry = Monoclinic prismatic<br/>]: (2/m) <br/>]: P 2/a
			\| unit cell = a = 11.737 Å, b = 5.171 Å, c = 7.63 Å; β = 112.54°; Z = 2
			\| color = Colorless, grey, yellow, pink, to white
			\| habit = Tabular prismatic crystals and columnar masses
			\| system = ]
			\| twinning = Common on {001}, lamellar
			\| cleavage = Perfect on {001}, poor on {201} with 38.5° angle between the two
			\| fracture = Subconchoidal
			\| tenacity = Brittle
			\| mohs = 6 - 6.5
			\| luster = Vitreous, pearly on cleavages
			\| refractive = n<sub>α</sub>=1.504, n<sub>β</sub>=1.510, n<sub>γ</sub>=1.516
			\| opticalprop = Biaxial (+)
			\| birefringence = δ = 0.012
			\| 2V = 82 – 84° measured
			\| pleochroism =
			\| streak = Colorless
			\| gravity = 2.4
			\| density =
			\| melt = 1350 °C<ref>{{cite web\|title=Petalite\|url=http://digitalfire.com/4sight/material/petalite_1114.html\|publisher=Digital Fire\|accessdate=23 October 2011}}</ref>
			\| fusibility = 5
			\| diagnostic =
			\| solubility = Insoluble
			\| diaphaneity = Transparent to translucent
			\| other =
			\| references = <ref name=HBM></ref><ref name=Webmin></ref><ref name=Mindat></ref><ref name=Klein>*Hurlbut, Cornelius S. and Klein, Cornelis, 1985, ''Manual of Mineralogy,'' Wiley, 20th ed., pp. 459-460 ISBN 0-471-80580-7</ref>
			}}

			'''Petalite''', also known as '''castorite''', is a ] ] ] ] ]]]<sub>4</sub>]<sub>10</sub>, crystallizing in the ] system. Petalite is a member of the ] group. It occurs as colourless, grey, yellow, yellow grey, to white tabular crystals and columnar masses. Occurs in lithium-bearing ]s with ], ], and ]. Petalite is an important ore of lithium, and is converted to ] and ] by heating to ~500 °C and under 3 kbar of pressure in the presence of a dense hydrous alkali borosilicate fluid with a minor carbonate component.<ref>{{cite book\|first=W. A. Deer\|title=Framework silicates: silica minerals, feldspathoids and the zeolites\|year=2004\|publisher=Geological Soc.\|location=London\|isbn=1-86239-144-0\|pages=296\|edition=2. ed.}}</ref> The colorless varieties are often used as ]s.
			]
			Discovered in 1800, type locality: ], ], ]. The name is derived from ] petalon for ''leaf''.<ref name=Mindat/>

			==References==
			{{Reflist}}

			{{Commons category}}
			{{Wikisource1911Enc}}

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			]


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Revision as of 20:46, 1 December 2012

Petalite
Petalite from Minas Gerais State, Brazil (size: 3x4 cm)
General
Category	Tectosilicate
Formula (repeating unit)	LiAlSi₄O₁₀
Strunz classification	09.EF.05
Crystal system	Monoclinic
Space group	Monoclinic prismatic H-M symbol: (2/m) Space group: P 2/a
Unit cell	a = 11.737 Å, b = 5.171 Å, c = 7.63 Å; β = 112.54°; Z = 2
Identification
Color	Colorless, grey, yellow, pink, to white
Crystal habit	Tabular prismatic crystals and columnar masses
Twinning	Common on {001}, lamellar
Cleavage	Perfect on {001}, poor on {201} with 38.5° angle between the two
Fracture	Subconchoidal
Tenacity	Brittle
Mohs scale hardness	6 - 6.5
Luster	Vitreous, pearly on cleavages
Streak	Colorless
Diaphaneity	Transparent to translucent
Specific gravity	2.4
Optical properties	Biaxial (+)
Refractive index	n_α=1.504, n_β=1.510, n_γ=1.516
Birefringence	δ = 0.012
2V angle	82 – 84° measured
Melting point	1350 °C
Fusibility	5
Solubility	Insoluble
References

Petalite, also known as castorite, is a lithium aluminium tectosilicate mineral Li Al Si₄O₁₀, crystallizing in the monoclinic system. Petalite is a member of the feldspathoid group. It occurs as colourless, grey, yellow, yellow grey, to white tabular crystals and columnar masses. Occurs in lithium-bearing pegmatites with spodumene, lepidolite, and tourmaline. Petalite is an important ore of lithium, and is converted to spodumene and quartz by heating to ~500 °C and under 3 kbar of pressure in the presence of a dense hydrous alkali borosilicate fluid with a minor carbonate component. The colorless varieties are often used as gemstones.

Petalite from Paprok, Nuristan Province, Afghanistan (size: 7.3 x 2.9 x 2.4 cm)

Discovered in 1800, type locality: Utö Island, Haninge, Stockholm, Sweden. The name is derived from Greek petalon for leaf.

References

"Petalite". Digital Fire. Retrieved 23 October 2011.
Handbook of Mineralogy
Webmineral
^ Mindat
*Hurlbut, Cornelius S. and Klein, Cornelis, 1985, Manual of Mineralogy, Wiley, 20th ed., pp. 459-460 ISBN 0-471-80580-7
Framework silicates: silica minerals, feldspathoids and the zeolites (2. ed. ed.). London: Geological Soc. 2004. p. 296. ISBN 1-86239-144-0. {{cite book}}: |edition= has extra text (help); |first= missing |last= (help)

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