Mineral Information and Data:

Mg6Si4O10(OH)8 [CNMNC approved formula]

Named from the Greek klino - "oblique" and chloros - "green".

IMA status : Valid species (Pre-IMA 1851) Grandfathered
(8th edition) :  
  (71) Phyllosilicate Sheets of Six-Membered Rings
  (71.04) interlayered 1:1, 2:1, and octahedra
  (71.04.01) Chlorite group (Tri-Dioctahedral)
(10th edition) :
  (09) Silicates
  (09.E) Phyllosilicates
  (09.EC) Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: B2/m
Unit cell: a = 5.35Å, b = 9.267(5) Å, c = 14.27(1) Å β = 97.13°
Crystal Habit: In thin to thick pseudohexagonal crystals, with tapering pyramidal faces, to 10 cm. Commonly foliated, fibrous, granular, earthy, massive.
Twinning: Twin plane {001}; twin axis [310], composition plane {001}
Color: Grass-green, olive-green, yellowish, white; pink, rose-red; colorless to pale green or yellow in thin section
Diaphaneity: Transparent to translucent
Luster: Pearly, greasy, dull
Hardness (Mohs): 2 - 2.5
Measured Density: 2.60 - 3.02 g/cm3
Cleavage: {001}, perfect
Tenacity: Laminae flexible, inelastic.
Streak: Greenish white to white
Polymorphism and Series: Forms a series with chamosite; stacking disorder is common.
Geologic Setting: A hydrothermal alteration product of amphiboles, pyroxenes, biotite. In chlorite schists, serpentinites, marbles, calc-silicate rocks, amphibolites, less commonly in ultramafic rocks. In ore veins; a detrital component of sediments.
Mineral Association: Serpentine, calcite, dolomite, actinolite, biotite, olivine, plagioclase, talc, chromite, uvarovite
Other Properties: Gemstone Extremely Rare.


Olive-green clinochlore crystals
Origin: Tilly Foster Mine, Brewster, Putnam County, New York, U.S.A.
Sample size: 5.5 x 3 x 2.5 cm
Photo: Rob Lavinsky


(zoom-in of above)