Petalite

Petalite
Petalite from Minas Gerais State, Brazil (size: 3x4 cm)
General
Category	Phyllosilicate
Formula	LiAlSi4O10
IMA symbol	Ptl [1]
Strunz classification	9.EF.05
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2/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	nα = 1.504, nβ = 1.510, nγ = 1.516
Birefringence	δ = 0.012
2V angle	82–84° measured
Melting point	1350 °C [2]
Fusibility	5
Solubility	Insoluble
References	[3] [4] [5] [6]

Petalite, also known as castorite, is a lithium aluminum phyllosilicate ^[7] mineral Li Al Si ₄ O ₁₀, crystallizing in the monoclinic system. Petalite occurs as colorless, pink, grey, yellow, yellow grey, to white tabular crystals and columnar masses. It 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. ^[8] Petalite (and secondary spodumene formed from it) is lower in iron than primary spodumene, making it a more useful source of lithium in, e.g., the production of glass. The colorless varieties are often used as gemstones. ^{[ citation needed ]}

Discovery and occurrence

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

Petalite was discovered in 1800, by Brazilian naturalist and statesman Jose Bonifacio de Andrada e Silva. Type locality: Utö Island, Haninge, Stockholm, Sweden. The name is derived from the Greek word petalon, which means leaf, alluding to its perfect cleavage. ^{[5] [9] [10]}

Economic deposits of petalite are found near Kalgoorlie, Western Australia; Aracuai, Minas Gerais, Brazil; Karibib, Namibia; Manitoba, Canada; and Bikita, Zimbabwe.

The first important economic application for petalite was as a raw material for the glass-ceramic cooking ware CorningWare.^{[ citation needed ]} It has been used as a raw material for ceramic glazes.

References

1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
2. "Petalite". Digital Fire. Retrieved 23 October 2011.
3. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Petalite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 14 March 2022.
4. Webmineral
5. "Petalite". Mindat.org .
6. • Hurlbut, Cornelius S. and Klein, Cornelis, 1985, Manual of Mineralogy, Wiley, 20th ed., pp. 459–460 ISBN   0-471-80580-7
7. Nickel, Ernest H.; Nichols, Monte C. "IMA/CNMNC List of Mineral Names" (PDF). Internet Archive. Materials Data, Inc. Archived from the original (PDF) on 20 March 2009. Retrieved 12 December 2024.
8. Deer, W. A. (2004). Framework silicates: silica minerals, feldspathoids and the zeolites (2. ed.). London: Geological Soc. p. 296. ISBN   978-1-86239-144-4.
9. D'Andraba (1800). "Des caractères et des propriétés de plusieurs nouveaux minérauxde Suède et de Norwège , avec quelques observations chimiques faites sur ces substances". Journal de Physique, de Chimie, d'Histoire Naturelle, et des Arts. 51: 239.
10. Sowerby, James (1811). Exotic mineralogy: Or, Coloured figures of foreign minerals: As a supplement to British mineralogy.

External links

• Media related to Petalite at Wikimedia Commons
• "Petalite"  . Encyclopædia Britannica . Vol. 21 (11th ed.). 1911.