OLIVINE GROUP OF MINERALS

MINERALOGY

1. OLIVINE GROUP

2. 1. Introduction. 2. Olivine Group 3. Geological occurrence of Olivine 4 . Physical Properties 5 . Optical Properties 6 . Members Under Olivine Group 7. Uses 8. Weathering 9. Conclusion 10. Bibliography CONTENTS

3. Name – Kaijirsong Rongpi Roll No - 377 B.sc 2 nd Semester Geology Department Aryavidyapeeth College,Guwahati Presentation on Olivine group

4. The Evolution of the term ‘OLIVINE’ is complex. The earliest name given to an Olivine group species was Chrysolite and was named by Johan Gottschalk Wallerius in 1747, although the name Chrysolite was later used by Balthasar George Sage in 1777 for what is now known as Prehnite. Chrysolite was renamed Olivine in 1789 by Abraham Gottlieb Werner for the usual Olive green color of this mineral. The second member of the group was named tephroite in 1823 by Johann Friedrich August Breithaupt. The commom Mg-dominant member of the group was renamed F orsterite by Serve-Dieu Abailard Levy in 1824. Hemy C. Salmon in 1859 explicitly used “olivine group” to designate minerals which were chemically analogous to Olivine. In the USA, J ames Dwight Dana and George Jarvis Brush began organizing groups in their system and organized the “Chrysolite group” in 1868 and that group name was continued into 1892 by Edward Salisbury Dana. The Universal Acceptance of “ Olivine Group ” occurred in the T wentieth Century. INTRODUCTION

5. Olivine is a magnesium iron silicate with the formula (Mg 2+ ,Fe 2+ ) 2 SiO 4 Thus it is a type of nesosilicate. It is a common mineral in Earth’s subsurface but weathers quickly on the surface. The two minerals Fayalite and Forsterite are referred to as the Olivine Series These are also the end-members of this olivine group and the melting temperature of F ayalite is about 1900 centigrade where this F ayalite ; melting temperature is higher than Forsterite. This is a group of rock-forming silicates that are typically found in mafic and ultramafic igneous rocks such as basalt, gabbro, dunite, diabase and peritodite. The minerals are olive green or brown in color. All these minerals crystallize in orthorhombic system OLIVINE GROUP

6. Most olivine are found at earth’s surface is in dark-colored igneous rocks. It usually crystallizes in the presence of plagioclase and pyroxene to form gabbro or basalt. These types of rocks are most common at divergent plate boundaries and at hot spots within the centers of tectonic plates. Olivine has a very high crystallization temperature compared to other minerals. That makes it one of the first minerals to crystallize from a magma. During the slow cooling of a magma, crystals of olivine may form and then settle to the bottom of the magma chamber because of their relatively high density. This concentrated accumulation of olivine can result in the formation of olivine-rich rocks such as dunite in the lower parts of a magma chamber. Crystals of olivine are sometimes formed during the metamorphism of a dolomite. The dolomite contributes magnesium and silica which is obtained from quartz and other impurities in the limestone. When olivine is metamorphosed it is transformed to serpentine GEOLOGICAL OCCURRENCE OF OLIVINE

7. During metamorphism, olivine is altered to serpentine (amphibole).

8. 1. Color – Olive Green, but can be yellow-green to bright green 2. Crystal Habit – Massive to Granular 3. Cleavage – Poor Cleavage 4. Fracture – Conchoidal 5. Hardness – 6.5 to 7 6. Luster – Vitreous 7. Streak – Colorless 8. Diaphaneity – Transparent to Translucent 9. Specific Gravity – 3.2 to 4.4 10. Crystal System – Orthorhombic PHYSICAL PROPERTIES

9. Color – Colorless and non pleochroic Refractive index – High positive relief, high refractive index Birefringence – Strong (0.037) Extinction - Straight OPTICAL PROPERTIES

10. Calcio-Olivine Ca 2 SiO 4 Fayalite Fe 2+ 2 SiO 4 Forsterite Mg 2 SiO 4 Glaucochroite CaMn 2+ SiO4 Kirschsteinite CaFe 2+ SiO 4 Laihunite Fe 2+ Fe 3+ 2 (SiO 4 ) 2 Liebenbergite ( Ni, Mg) 2 SiO 4 Monticellite CaMgSiO 4 Olivine ( Mg 2+ ,Fe 2+ ) 2 SiO 4 Roepperite ( Fe 2+ 2, Mn,Zn)SiO 4 Tephroite Mn 2+ 2 SiO 4 MEMBERS UNDER THE OLIVINE GROUP

11. Forsterite It is green in color or pale yellow sometimes And it is of vitreous luster Fracture is conchoidal with streak white. Common impurities present in this mineral is Fe.

12. Fayalite Its color is of yellow or brown or greenish-yellow. Streak is of colorless and common impurities present is of Mn. It is also known Iron-Chrysolite

13. Glauchochroite Its color is of bluish grey and pink or brown or white. Vitreous luster with opaque transparency Common impurities present in here are of Fe, Zn , Pb and Mg. It is also called as Calcotephroite.

14. Common impurities present in here are Ti,Al,Mn,Mg,Na,K and P Chemical Formula is CaFe 2+ SiO 4 It is also known lime-iron olivine. Kirschsteinite

15. In this minerals, there is an impurities of Fe and Co. Liebenbergite

16. Laihunite T he color of this mineral is of Dark brown. Streak is of brown. Impurities present are of Mg and Ca.

17. Monticellite Its color is of colorless , grey or greenish sometimes and of vitreous luster

18. It is grey or reddish brown in color ,vitreous luster and streak is of pale grey Tephroite

19. Olivine minerals are common in igneous rocks. P eridotite B asalt G abbro

20. Olivine is common in meteorites. Olivine was brought back to Earth from Comet Wild by NASA’s Stardust mission.

21. Olivine is the gemstone Peridot. It has been a human favorite for centuries, and is often used as a birthstone for August.

22. Olivine minerals are used in industry as abrasives . Olivine is used in steel manufacturing. USES

23. Olivine is not only used in industry but most O livine is used in metallurgical processes as a slag-conditioner. High Magnesium Olivine (Forsterite) is added to lash furnaces to remove impurities from steel and to form a slag. Olivine has also been used as a refractory material. It is used to make refractory brick and used as a casting sand. Both of these uses are in decline as alternative materials are less expensive and easier to obtain . Olivine is the green in green sand beaches.

24. WEATHERING Olivine is one of the weaker common minerals on the surface according to the goldich dissolution series. It alters into Iddingsite readily in the presence of water. Artificially increasing the weathering rate of olivine . The presence of Iddingsite on Mars would suggest that liquid water once existed there, and might enable scientists to determine when there was last liquid water on the planet.

25. Olivine minerals tend to break down (weather) very easily at the Earth’s surface. The iron and magnesium released by this weathering process helps to make volcanic soils very fertile.

26. From the above mentioned theme’ Olivine”, we came to know that Olivine Group consist of lots of minerals in it i.e. Fayalite , Forsterite etc Olivine are common in jewelry or as a gemstones Weathering process also plays an important role where olivine could break the earth’s surface very easily. CONCLUSION

27. http://www.wikipedia.com/olivinegroup A textbook of Mineralogy by G.B Mahapatra http://www.slideshare.net.com/olivine A textbook of Geology by P.K Mukerjee http://www.geology.com/olivinegroup http:// www.mindat.org/olivinegroup A manual of mineralogy by Dexter and Perkins Bibliography

28. Thank You