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Chlorite

Chlorite is the organization name for approximately 10 related minerals. However, the time period Chlorite may be used each to explain the organization in fashionable, or as a specific term to explain any inexperienced member of the Chlorite institution whose precise identity isn’t always realistic to be decided. Although Chlorite isn’t diagnosed as an person mineral species through the IMA, mineral creditors nonetheless talk over with it by its conventional call, except whilst in particular regarding the person member minerals together with Clinochlore, Chamosite, and Cookeite.

Name: Chlorite is derived from a Greek word meaning green, in allusion to the common color of the mineral.

Diagnostic Features: Characterized by its green color, micaceous habit and cleavage, and by the fact that the folia are not elastic.

Composition: Hydrous iron-magnesium aluminum silicate. Mg5Al2- Si3Oio(OH)8 is the formula for clinochlore. Ferrous iron may be present. Penninite is essentially the same; prochlorite has less silicon and usually contains iron.

Chlorite Occurrence

is usually determined in igneous rocks as an alteration product of mafic minerals together with pyroxene, amphibole, and biotite. In this environment chlorite may be a retrograde metamorphic alteration mineral of present ferromagnesian minerals, or it could be present as a metasomatism product through addition of Fe, Mg, or different compounds into the rock mass. Chlorite is a not unusual mineral related to hydrothermal ore deposits and normally takes place with epidote, sericite, adularia and sulfide minerals. Chlorite is also a commonplace metamorphic mineral, typically indicative of low-grade metamorphism. It is the diagnostic species of the zeolite facies and of decrease greenschist facies. It occurs within the quartz, albite, sericite, chlorite, garnet assemblage of pelitic schist. Within ultramafic rocks, metamorphism also can produce predominantly clinochlore chlorite in affiliation with talc.

Members of the Chlorite group

Baileychlore(Zn,Fe+2,Al,Mg)6(Al,Si)4O10(O,OH)8
Chamosite(Fe,Mg)5Al(Si3Al)O10(OH)8
Clinochlore(Mg,Fe2+)5Al(Si3Al)O10(OH)8
CookeiteLiAl4(Si3Al)O10(OH)8
DonbassiteAl2[Al2.33][Si3AlO10](OH)8
Gonyerite(Mn,Mg)5(Fe+3)2Si3O10(OH)8
Nimite(Ni,Mg,Al)6(Si,Al)4O10(OH)8
Odinite(Fe,Mg,Al,Fe,Ti,Mn)2.4(Al,Si)2O5OH4
Orthochamosite(Fe+2,Mg,Fe+3)5Al(Si3Al)O10(O,OH)8
Pennantite(Mn5Al)(Si3Al)O10(OH)8
Ripidolite(Mg,Fe,Al)6(Al,Si)4O10(OH)8
SudoiteMg2(Al,Fe)3Si3AlO10(OH)8

Physical Properties of Chlorites

Chemical ClassificationSilicate
ColorVarious shades of green. Rarely yellow, white, pink, black
StreakGreenish to greenish gray
LusterVitreous, pearly, dull
DiaphaneityTransparent, translucent, opaque
CleavagePerfect in one direction
Mohs Hardness2 to 3
Specific Gravity2.6 to 3.3
Diagnostic PropertiesColor, hardness, foliated appearance, feels slightly greasy
Chemical CompositionA generalized formula: (X,Y)4-6(Si,Al)4O10(OH,O)8

 

The “X” and “Y” in the formula represent ions, which might include: Fe+2, Fe+3, Mg+2, Mn+2, Ni+2, Zn+2, Al+3, Li+1, or Ti+4. The composition and physical properties of chlorites vary as these ions substitute for one another in solid solution.

Crystal SystemMonoclinic
UsesVery few industrial uses. Used as a filler and as a constituent of clay.

Members of the chlorite mineral organization are normally green in color, have a foliated look, best cleavage, and an oily or soapy sense. Their variable chemical composition offers them more than a few hardness and specific gravity. This makes them hard to differentiate in hand specimen.

Optical Properties of Chlorite

chlorite
Property
Value
Formula(Mg, Al, Fe)3 (Si,Al)4O10(OH)2.(Mg,Al,Fe)3(OH)6
Crystal Systemmonoclinic
Crystal HabitPseudohexagonal tabular crystals;commonly foliated, fibrous, granular, earthy or massive; twins on (001)
Cleavageperfect cleavage on {001}
Color/Pleochroismcolorless-pale green;
Pleochroic
Optic SignBiaxial positive/negative
2V0-60 (positive)
0-40 (negative)
Optic OrientationX or Z^a=0-9o
Y=b
optic plane (010)

Refractive Indices

alpha=1.55-1.67
beta =1.55-1.69
gamma =1.55-1.69
Max Birefringencerarely above first-order white or yellow
ExtinctionInclined
Distinguishing FeaturesGreen under plane polarized light, pleochroic, anomalous interference colors, weak birefringence, micaceous
References and LinksNesse, William D., 1986, Introduction to Optical Mineralogy: New York, Oxford University Press, 325 p.

 UCLA Mineral Library

EditorsSarah Cadieux (MHC ’08), Katherine Kravitz (’11)

Chlorite Uses

Chlorite is a mineral with a low capacity for industrial use. It does now not have physical properties that make it suited for a specific use, and it does not contain materials that make it a target of mining. When found, chlorite is commonly in detail intermixed with different minerals, and the fee of separation could be excessive. As a end result, chlorite isn’t always mined and processed for any precise use. Its foremost use is as a coincidental constituient in crushed stone.