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
|re|er}}| 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]

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.

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

## Discovery and occurrence

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]

## References

1. ↑ 1.0 1.1 Handbook of Mineralogy
2. ↑ Carpholite on Mindat.org
3. ↑ 3.0 3.1 Carpholite on Webmineral
4. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.

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