This document provides information on various members of the amphibole group of minerals. It begins with an introduction to amphiboles, noting their double chain silicate structure and presence in both igneous and metamorphic rocks. It then describes the distinguishing characteristics and chemical formulas of important orthorhombic amphiboles like anthophyllite and gedrite. Next, it covers the monoclinic amphiboles, detailing minerals in the cummingtonite, actinolite, and hornblende series as well as the sodium-bearing amphiboles glaucophane and riebeckite. Paragenesis and typical crystal habits are also discussed for each amphibole.

1. MEMBERS OF AMPHIBOLE GROUP
JFSHJL
GUIDED BY :
Dr. NARENDRA JOSHI
SUBMITTED BY:
KRITI RAI
M.Sc. 1st year
DEPARTMENT OF GEOLOGY
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2. CONTENT
•Introduction
•Orthorhombic amphiboles
Anthophyllite
Gederite
•Monoclinic amphiboles
Cummingtonite series :
Cummingtonite
Grunerite
Actinolite series :
Tremolite
Actinolite
Hornblende
Na-amphiboles :
Glaucophane
Riebeckite
•Reference
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3. INTRODUCTION
1. The term amphiboles is derived from the Greek word
‘’amphibolos’’ meaning Ambiguous.
2. Members of amphibole group of minerals occur in a
wide range of P-T environments and are comon
contituents of both igneous and metamorphic rocks.
3. Amphibole is the name of an important group of
generally dark coloured,inosilicates minerals,forming
prism or needle like crystals.
4. The essential feature of the structures of all
amphiboles is the presence of (Si,Al)O4 tetrahedra
linked to form chains which have double the width of
those in pyroxenes and have the composition
(Si,Al)O11.
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4. • Amphiboles have double chain structure extending
in the direction of C-axis or verticle axis.
• The amphiboles are a group of hydroxylated chain
silicates with some substitution of F and Cl for
(OH).
• Amphiboles include both orthorhombic and
monoclinic members.
• The amphiboles contain essential (OH) group in
the structure and the Si:O ratio is 4:11.
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5. DIFFERENCE BETWEEN AMPHIBOLE AND
PYROXENE
PROPERTIES AMPHIBOLE PYROXENE
Structure Double chained Single chained
Cleavage and prism angle 124
.
87
.
Change in colour pleochroic Non-pleochroic
Transverse section Six-sided Eight-sided
Extinction angle 16
.
48
.
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6. STRUCTURE OF AMPHIBOLE
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7. CLEAVAGE ANGLE ABOUT 124
.
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8. GENERAL FORMULA
The general formula for all the members of the
amphibole group can be written as
W(0-1) X2 Y5 Z8 O22 (OH,F)2 .
In which the symbols W,X,Y,Z indicate elements
having similar ionic radii and being capable of
replacing each other in the structure.
W stands for large cations Ca and Na sometimes k.X
for smaller cations Mg and Fe2+ sometimes Mn.Y
can be Fe,Mg, Mn and Z can be Si or Al.
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9. AMPHIBOLES
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10. ORTHORHOMBIC AMPHIBOLE
Mineral Chemical formula
Anthophyllite (Mg,Fe+2)7Si8O22(OH)2
Gederite (Mg,Fe+2)5Al2Si6Al2O22(OH)2
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11. ANTHOPHYLLITE
• Anthophyllite has prismatic form, two directional cleavage
and it is a colourless.
• Anthophyllite is a characteristic of metamorphic rocks. It is
the main constituent of anthophyllite schist and is also a
secondary mineral in peridotites and dunites.
• Anthophyllite is the principal contituent of mass-fiber
asbestos.
•Its typical forms are lamellar or fibrous.
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12. Anthophyllite
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13. GEDRITE
•Gedrite was first described for an occurrence in
gedres,France in 1836.
•Gedrite is a magnesium (Mg) rich endmember of
a solid solution series.
•Its typical forms are bladed, prismatic; fibrous
and sheath like aggregates.
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14. Gedrite
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15. PARAGENESIS
The orthorhombic amphiboles are unknown in
igneous rocks;anthophyllite and gederite occur in
contact and high to medium grade metamorphic rocks
in association with garnet, kyanite ,biotite and
cummingtonite.
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16. MONOCLINIC GROUP
MINERAL CHEMICAL FORMULA
cummintgonite (Mg,Fe)7Si8O22 (OH)2
grunerite Fe7Si8O22(OH)2
tremolite Ca2Mg5Si8O22(OH)2
actinolite Ca2 (Mg,fe)5Si8O22(OH)2
hornblende (K,Na)0-1 (Ca,Na,Fe,Mg)2
(Mg,Fe,Al)5 (Si,Al)8 O22(OH)2
glaucophane Na2Mg3Al2Si8O22(OH)2
riebeckite Na2 (Fe,Mg)3 (Fe,Al)2 Si8O22 (OH)2
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17. CUMMINGTONITE
• It was named after cummington, mussachusetts,
where it was first dicovered.
• It is brown in color and has columnar to fibrous and
granular form.
• It is perfectly prismatic.
• Its hardness is 5-6 .
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18. Cummingtonite
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19. PARAGENESIS
Cummingtonite is most commonly found in low-Ca
amphibolites. it is associated with common
hornblend, in some diorites. They also occur in some
silicic volcanic rocks.
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20. GRUNERITE
• It is named after L.E Gruner,a 19th century
mineralogist,who first analyzed grunerite.
• Grunerite is the name used for the minerals of the
cummingtonite- series in which iron greatly
predominates over magnesium.
• Its typical forms are fibrous, columner, asbestiform.
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21. Grunerite
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22. PARAGENESIS
Grunerite is product of metamorphism.it occurs in
metamorphic rocks like schists. It is also found with
Fe-rich minerals such as hematite,magnetite and
garnet in metamorphosed iron rich sediments.
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23. TREMOLITE
• It is named after Val Tremola,switzerland, where it was
first found.
• Trimolite is typically prismatic.
• Tremolite is one of the first mineral to form when
impure carbonate are metamorphosed.
• It is formed early by the reaction of dolomite and
quartz.
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24. Tremolite
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25. PARAGENESIS
Tremolite is essentially metamorphic mineral and
occur in both contact and regionally metamorphosed
rocks. It is a characteristic mineral in low grade
regionally metamorphosed ultrabasic rock such as
tremolite-talc and tremolite-carbonate-antigorite-
schist.it commnly occurs in dolomitic limestone.
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26. ACTINOLITE
•Named from the Greek ‘’actis’’ (ray), referring to its
common habit of radiating needles.
•It is characteristic of medium-grade metamorposed
mafic rocks.
•actinolite typically form needles-either radiating or in
parallel aggregates,or columnar masses.
•They are formed from the metamorphism of silicious
dolomites.
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27. Actinolite
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28. PARAGENESIS
Actinolite is also a metamorphic mineral. It is a
contituent of some glaucophane schists,and here is
associated particularly with albite, chlorite and
epidote. Actinolite is a common product of retrograde
metamorphism of basic rocks but with increasing
grade of metamorphism its content of aluminium
increases.
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29. HORNBLENDE
• The word hornblende is derived from the German horn
and blenden(blind),to ‘deceive’ in allusion to its
similarity in appearence to metal- bearing ore minerals.
• Habit, cleavages and dark color usually serve to identify
hornblende
• Habit may be massive or granular and has prismatic
cleavage.
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30. Hornblende
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31. PARAGENESIS
Hornblendes are particularly characteristics minerals
of intermediate plutonic rocks.they also occur by
primary crystallization in basic and ultrabasic rocks as
well as in rocks of acid and alkali ,also occurs in the
rocks of alkali basalt.it occurs commony in syenites
and diorites.
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32. GLAUCOPHANE
•Its name takes from the greek work meaning- ‘’to appear
bluish’’.
•It is a alkali basal tand it is iron poored of the series.
•Glaucophane is a high pressure metamorphic mineral
characteristic of blue schist facies.
•Accicular,asbestiform or fibrous habit characterizes
glaucophane.
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33. Glaucophane
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34. PARAGENESIS
Glaucophane schists, resulting from the
metamorphism of basaltic rocks,are usually located in
folded geosynclinal terrains and are commonly
associated with greenschists and epidote-
amphibolites.they are sometimes referred as
blueschists.
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35. RIEBECKITE
• Named after German explorer Emil Riebeck in 1888.
• Fiberous form of riebeckite is called crociodolite
and is one of the six recognised type of asbestos.
• Its Moh hardness is 5-6 , specific gravity 3-3.4 and
has uneven fracture.
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36. Riebeckite
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37. Crociodolite
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38. PARAGENESIS
Riebeckite is found in a few low-grade regionally
metamorphosed schists, and it may also occur in
authigenic environments.riebeckite is found in
granites and syenites, in microgranites and in acid
volcanic rocks.
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39. REFERENCES
• ZUSSMAN .J
• HOWIE R.A PAGE NO. 223-232
• DEER W.A
• Paul F.Kerr PAGE NO. 318-333
• ERNST W.G. PAGE NO. 40-80
• https://www.britannica.com/science/amphibole
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40. THANK YOU
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