Chlorite Group

Green Mountain Mine, Day Book, Yancey Co., North Carolina, USA
© 2002, Keith Wood

System:	Monoclinic	Hardness:	2 - 2½
A group of triclinic and monoclinic micaceous minerals with a structure consisting of T-O-T layers with two layers having their silicate tetrahedraal apices pointing towards each other, separated by an interlayer that may be simple octahedrally coordinated cations or which may be a brucite-like layer of two sheets of closely packed OH groups with the interstices between sheets providing the octahedral cordination site; the T-O-T layers and interlayer are bonded by electrostatic and hydrogen bonding forces; as the "a" and "b" directions of the T-O-T layer may be oriented to the interlayer "a" and "b" directions in twelve different stacking sequences, resulting in twelve different polytype possibilities (not all of which have been found in Nature yet for each species). The general formula may be stated A^5-6T^4O^10-Z^8, where A = Al, Fe#2+, Fe#3+, Li, Mg, Mn, or Ni, while T = Al, Fe#3+, Si, or a combination of them, and Z = O and/or OH.

Classification of Chlorite Group

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Physical Properties of Chlorite Group

Streak:

Colorless

Hardness (Mohs):

2 - 2½

Density (measured):

2.6 - 3.3 g/cm³

Crystallography of Chlorite Group

Crystal System:

Monoclinic

Other Names for Chlorite Group

Synonyms:

Esperanto names:

German names:

Russian names:

Хлорит

Spanish names:

Chlorita

Traditional Chinese names:

绿泥石

Varieties:

Brunsvigite

Prasolite

Other Information

Health Warning:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Chlorite Group

Reference List:

Dodge, F.C.W. (1973), Chlorites from the granitic rocks of the central Sierra Nevada batholith: Mineralogical Magazine: 39: 58-64.

Post, J.L. and Janke, N.C. (1974) Properties of “swelling chlorite” in some Mesozoic formations of California. Lays and Clay Minerals: 22: 67-77.

Hazen, R.M. and Finger, L.W. (1978) The crystal structures and compressibilities of layer minerals at high pressure. II. Phlogopite and chlorite. American Mineralogist: 63: 293-296.

Spinnler, G.E. (1985) HRTEM study of antigorite, pyroxene-serpentine reactions and chlorite, 248 p. PhD Thesis, Arizona State University, Tempe, Arizona.

Schreyer, W., Franslet, A.M., and Abraham, K. (1986) A miscibility gap in trioctahedral Mn-Mg-Fe chlorites: evidence from the Lienne Valley manganese deposit, Ardennes, Belgium. Contributions to Mineralogy and Petrology: 94: 333-342.

Li, G., Peacor, D.R., and Essene, E.J. (1998) The formation of sulfides during alteration of biotite to chlorite-corrensite. Clays and Clay Minerals: 46: 649-657.

Lougear, A., M. Grodzicki, C. Bertoldi, A.X. Trautwein, K. Steiner, and G. Amthauer (2000), Mössbauer and molecular orbital study of chlorites: Physica and Chemistry of Minerals: 27: 258-269.

Bertoldi, C., Benisek, A., Cemi?, L., and Dachs, E. (2001) The heat capacity of two natural chlorite group minerals derived from differential scanning calorimetry. Physics and Chemistry of Minerals: 28: 332-336.