Chesterite

Chesterite
General
Category	Silicates, silicate germanates, inosilicates (multiple chains)
Chemical formula	(Mg,Fe)17Si20O54(OH)6
Crystal symmetry	orthorhombic, mm2, A21ma
Unit cell	a = 18.61Å, b = 45.3Å, c = 5.29Å, V=4,459.64 ų
Identification
Molar mass	2,074.96 gm
Color	Colorless, pink, brown
Crystal system	orthorhombic, prismatic
Cleavage	(110) perfect
Mohs scale hardness	2-2.5
Luster	Silky - Pearly
Streak	White
Density	3.23
Optical properties	Biaxial negative, α=1.617, β=1.632, γ=1.64, 2V=70°
Refractive index	1.64-1.67
Birefringence	δ = 0.023
Pleochroism	weak, pink-brown
References	[1][2][3]

Chesterite ((Mg,Fe)₁₇Si₂₀O₅₄(OH)₆) is a type of silicate mineral that can be compared to amphiboles, micas, and jimthompsonite^[1]. Chesterite is named after Chester, Vermont, where it was first discovered^[4]. The specific geologic setting within its origin is the Carleton talc quarry in Chester, Vermont^[2]. Chesterite has an orthorhombic crystal structure, which means it has three crystallographic axes of unequal length. All of the axes are perpendicular to each other. The stacking sequence for Chesterite, which is found in micas, is very similar to orthopryoxenes and orthoamphiboles^[3][5]. Chesterite is an anisotropic mineral; therefore, it allows light to travel through it at different velocities when viewed at different angles.^[2]. Chesterite is usually found in thin sheets in between ultra-mafic rocks^[2]. A polytype of chesterite could possibly be anthophyllite, which has a similar crystal structure.^[5]. Chesterite is used for research on stacking formations and symmetry point groups that could be possible polymorphs or polysomes of the amphibole-anthophyllite groups^[3]. Chesterite has no direct purpose or usage, but some geologists or scientists generally classify it under the amphibole-anthophyllite group. With that general classification, chesterite could possibly be used for the same purpose as amphibole and anthophyllite, asbestos, but that is just a speculation.^[4][6].

References

1. ^ ^{a b} Ralph, Joylon and Ida, Chau. "Chesterite." http://www.mindat.org/min-997.html.
2. ^ ^{a b c d} "Chesterite Mineral Data." http://webmineral.com/data/Chesterite.shtml. Accessed 3 November 2010.
3. ^ ^{a b c} Veblen, D.R. and Burnham, C.W. (1978) New biopyriboles from Chester, Vermont: II. The crystal chemistry of jimthompsonite, clinojimthompsonite, and Chesterite, and the amphibole-mica reaction. American Mineralogist, 63, 1053-1073.
4. ^ ^{a b} Konishi, Hiromi, Reijo, Alviola, and Buseck, Peter R. (2004) 2111 biopyribole intermediate between pyroxene and amphibole: Artifact or natural product? American Mineralogist, 89, 15-19.
5. ^ ^{a b} Wyckoff, R.W.G. (1968) Crystal Structures (Second edition). 310-314 p. University of Arizona, Tucson, Arizona.
6. ^ Lamb, Thomas J, "A Closer Look at Asbestos Fibers." http://www.asbestos-mesothelioma.com/asbestos-fibers.html. Accessed 21 November 2010.