MEMBERS OF AMPHIBOLE GROUP

AMPHIBOLE GROUP

1. MEMBERS OF AMPHIBOLE GROUP JFSHJL GUIDED BY : Dr. NARENDRA JOSHI SUBMITTED BY: KRITI RAI M.Sc. 1 st year DEPARTMENT OF GEOLOGY 9/28/2019 1

2. CONTENT I ntroduction O rthorhombic amphiboles A nthophyllite G ederite Monoclinic amphiboles C ummingtonite series : C ummingtonite G runerite A ctinolite series : T remolite A ctinolite H ornblende Na-amphiboles : G laucophane R iebeckite R eference 9/28/2019 2

3. INTRODUCTION T he term amphiboles is derived from the Greek word ‘’amphibolos’’ meaning Ambiguous. M embers of amphibole group of minerals occur in a wide range of P-T environments and are comon contituents of both igneous and metamorphic rocks. A mphibole is the name of an important group of generally dark coloured,inosilicates minerals,forming prism or needle like crystals. T he essential feature of the structures of all amphiboles is the presence of (Si,Al)O 4 tetrahedra linked to form chains which have double the width of those in pyroxenes and have the composition (Si,Al)O 11. 9/28/2019 3

4. A mphiboles 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. T he amphiboles contain essential (OH) group in the structure and the Si:O ratio is 4:11. 9/28/2019 4

5. DIFFERENCE BETWEEN AMPHIBOLE AND PYROXENE PROPERTIES AMPHIBOLE PYROXENE S tructure D ouble chained Single chained Cleavage and prism angle 124 . 87 . Change in colour pleochroic N on-pleochroic Transverse section S ix-sided E ight-sided Extinction angle 16 . 48 . 9/28/2019 5

6. STRUCTURE OF AMPHIBOLE 9/28/2019 6

7. CLEAVAGE ANGLE ABOUT 124 . 9/28/2019 7

8. GENERAL FORMULA The general formula for all the members of the amphibole group can be written as W (0-1) X 2 Y 5 Z 8 O 22 (OH,F) 2 . I n 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 Fe 2+ sometimes Mn.Y can be Fe,Mg, Mn and Z can be Si or Al. 9/28/2019 8

9. AMPHIBOLES 9/28/2019 9

10. ORTHORHOMBIC AMPHIBOLE Mineral Chemical formula Anthophyllite (Mg,Fe +2 ) 7 Si 8 O 22 (OH) 2 Gederite (Mg,Fe +2 ) 5 Al 2 Si 6 Al 2 O 22 (OH) 2 9/28/2019 10

11. ANTHOPHYLLITE Anthophyllite has prismatic form, two directional cleavage and it is a colourless. A nthophyllite is a characteristic of metamorphic rocks. I t is the main constituent of anthophyllite schist and is also a secondary mineral in peridotites and dunites. A nthophyllite is the principal contituent of mass-fiber asbestos. I ts typical forms are lamellar or fibrous. 9/28/2019 11

12. Anthophyllite 9/28/2019 12

13. G EDRITE G edrite was first described for an occurrence in gedres,France in 1836. G edrite is a magnesium (Mg) rich endmember of a solid solution series. I ts typical forms are bladed, prismatic; fibrous and sheath like aggregates. 9/28/2019 13

14. G edrite 9/28/2019 14

15. PARAGENESIS T he 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. 9/28/2019 15

16. MONOCLINIC GROUP MINERAL CHEMICAL FORMULA cummintgonite (Mg,Fe) 7 Si 8 O 22 (OH) 2 grunerite Fe 7 Si 8 O 22 (OH) 2 tremolite Ca 2 Mg 5 Si 8 O 22 (OH) 2 actinolite Ca 2 (Mg,fe) 5 Si 8 O 22 (OH) 2 hornblende (K,Na) 0-1 (Ca,Na,Fe,Mg) 2 (Mg,Fe,Al) 5 (Si,Al) 8 O 22 (OH) 2 glaucophane Na 2 Mg 3 Al 2 Si 8 O 22 (OH) 2 riebeckite Na 2 (Fe,Mg) 3 (Fe,Al) 2 Si 8 O 22 (OH) 2 9/28/2019 16

17. CUMMINGTONITE I t was named after cummington, mussachusetts, where it was first dicovered. I t is brown in color and has columnar to fibrous and granular form. I t is perfectly prismatic. I ts hardness is 5-6 . 9/28/2019 17

18. Cummingtonite 9/28/2019 18

19. PARAGENESIS C ummingtonite is most commonly found in low-Ca amphibolites. it is associated with common hornblend, in some diorites. T hey also occur in some silicic volcanic rocks. 9/28/2019 19

20. GRUNERITE I t is named after L.E Gruner,a 19 th century mineralogist,who first analyzed grunerite. G runerite is the name used for the minerals of the cummingtonite- series in which iron greatly predominates over magnesium. I ts typical forms are fibrous, columner, asbestiform. 9/28/2019 20

21. Grunerite 9/28/2019 21

22. PARAGENESIS Grunerite is product of metamorphism.it occurs in metamorphic rocks like schists. I t is also found with Fe-rich minerals such as hematite,magnetite and garnet in metamorphosed iron rich sediments. 9/28/2019 22

23. TREMOLITE I t is named after Val Tremola,switzerland, where it was first found. T rimolite is typically prismatic. T remolite is one of the first mineral to form when impure carbonate are metamorphosed. I t is formed early by the reaction of dolomite and quartz. 9/28/2019 23

24. Tremolite 9/28/2019 24

25. PARAGENESIS T remolite is essentially metamorphic mineral and occur in both contact and regionally metamorphosed rocks. I t 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. 9/28/2019 25

26. ACTINOLITE N amed from the Greek ‘’actis’’ (ray), referring to its common habit of radiating needles. I t is characteristic of medium-grade metamorposed mafic rocks. actinolite typically form needles-either radiating or in parallel aggregates,or columnar masses. T hey are formed from the metamorphism of silicious dolomites. 9/28/2019 26

27. Actinolite 9/28/2019 27

28. PARAGENESIS A ctinolite is also a metamorphic mineral. I t is a contituent of some glaucophane schists,and here is associated particularly with albite, chlorite and epidote. A ctinolite is a common product of retrograde metamorphism of basic rocks but with increasing grade of metamorphism its content of aluminium increases. 9/28/2019 28

29. HORNBLENDE T he 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. H abit, cleavages and dark color usually serve to identify hornblende H abit may be massive or granular and has prismatic cleavage. 9/28/2019 29

30. Hornblende 9/28/2019 30

31. PARAGENESIS H ornblendes 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. 9/28/2019 31

32. GLAUCOPHANE I ts name takes from the greek work meaning- ‘’to appear bluish’’. I t is a alkali basal tand it is iron poored of the series. G laucophane is a high pressure metamorphic mineral characteristic of blue schist facies. A ccicular,asbestiform or fibrous habit characterizes glaucophane. 9/28/2019 32

33. Glaucophane 9/28/2019 33

34. PARAGENESIS G laucophane 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. 9/28/2019 34

35. RIEBECKITE N amed after German explorer Emil Riebeck in 1888. F iberous form of riebeckite is called crociodolite and is one of the six recognised type of asbestos. I ts M oh hardness is 5-6 , specific gravity 3-3.4 and has uneven fracture. 9/28/2019 35

36. Riebeckite 9/28/2019 36

37. Crociodolite 9/28/2019 37

38. PARAGENESIS R iebeckite 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. 9/28/2019 38

39. REFERENCES ZUSSMAN .J HOWIE R.A PAGE NO. 223-232 DEER W.A P aul F.Kerr PAGE NO. 318-333 ERNST W.G. PAGE NO. 40-80 https://www.britannica.com/science/amphibole 9/28/2019 39

40. THANK YOU 9/28/2019 40