Carpholite

Carpholite is a manganese silicate mineral with formula Mn²⁺Al₂Si₂O₆(OH)₄. It occurs as yellow clusters of slender prisms or needles. It crystallizes in the orthorhombic system.

Carpholite
General
Category	Inosilicate
Formula (repeating unit)	Mn2+Al2Si2O6(OH)4
Strunz classification	9.DB.05
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Ccca
Unit cell	a = 13.83, b = 20.31, c = 5.13 [Å]; Z = 8
Identification
Color	Yellow
Crystal habit	Prismatic, acicular to fibrous clusters
Twinning	On {100}
Cleavage	Perfect on {010}
Tenacity	Brittle
Mohs scale hardness	5.5-6
Luster	Silky
Diaphaneity	Translucent
Specific gravity	2.935-3.031
Optical properties	Biaxial (-)
Refractive index	nα = 1.610 nβ = 1.628 nγ = 1.630
Birefringence	δ = 0.020
Pleochroism	Distinct; X = Y = pale yellow; Z = colorless
References	[1][2][3]

The carpholite group includes ferrocarpholite, magnesiocarpholite, vanadiocarpholite, and potassiccarpholite.

Discovery and occurrenceEdit

It was first described in 1817 for an occurrence in Horní Slavkov (Schlaggenwald), Karlovy Vary Region, Bohemia. The name derives from Greek karfos for "straw" and lithos for "stone" due to its crystal habit.^[3]

Its typical occurrence is in shales that have undergone low grade metamorphism. Associated minerals include sudoite, manganoan garnet, chloritoid and fluorite.^[1]

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License