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Clinozoisite, Amphibole Group - Mount Belvidere Quarries, Vermont, USA.jpg
Category Sorosilicates
Epidote group
(repeating unit)
Strunz classification 9.BG.05a
Dana classification 58.2.1a.4
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/m
Unit cell a = 8.879, b = 5.583
c = 10.155 [Å]; β = 115.50°; Z = 2
Color Colorless, green, gray, light green, yellow green
Crystal habit Elongated primatic crystals, striated; granular to fibrous
Twinning Lamellar on {100} uncommon
Cleavage Perfect on {001}
Fracture Irregular/uneven
Tenacity Brittle
Mohs scale hardness 6-7
Luster Vitreous
Streak Grayish white
Diaphaneity Transparent to translucent
Specific gravity 3.3 - 3.4
Optical properties Biaxial (+)
Refractive index nα = 1.706 - 1.724 nβ = 1.708 - 1.729 nγ = 1.712 - 1.735
Birefringence δ = 0.006 - 0.011
2V angle 14 to 90° measured
References [1][2][3]

Clinozoisite is a complex calcium aluminium sorosilicate mineral with formula: Ca2Al3(Si2O7)(SiO4)O(OH). It forms a continuous solid solution series with epidote by substitution of iron(III) in the aluminium (m3 site) and is also called aluminium epidote.[1]

Clinothulite is a manganese bearing variety with a pinkish hue due to substitution of Mn(III) in the aluminium site.[4]

It was originally discovered in 1896 in East Tyrol, Austria, and is so-named because of its resemblance to zoisite and its monoclinic crystal structure.[1]

It occurs in rocks which have undergone low to medium grade regional metamorphism and in contact metamorphism of high calcium sedimentary rocks. It also occurs in saussurite alteration of plagioclase.[2]


  • Nesse, William D., "Introduction to Mineralogy," (c)2000 Oxford University Press ISBN 0-19-510691-1