Introduction; Chemical composition of garnet; Structure; Classification; Physical properties; Optical properties; Occurrences; Gem variety; and Uses Garnet group of minerals is one of the important group of minerals. Since they are found in wide variety of colours, they are also used as gemstones. Garnet group of minerals are also abrasives and thus have various industrial applications. 

1. 1
Garnet Group
Andradite
(Ca3Fe2Si3O12)
Hassan Z. Harraz
hharraz2006@yahoo.com
Spring 2018

2. Outline of Topic
• Introduction
• Chemical composition of garnet
• Structure
• Classification
• Physical properties
• Optical properties
• Occurrence
• Gem variety
• Uses
• Conclusion
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We will explore all of the above in Topic 3.

3. INTRODUCTION
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4. 4
CHEMICAL COMPOSITION of GARNET GRoup

5. 5

6. 6

7. 7

8. The Garnet Group
Almandine
Grossular
Andradite
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9. 9
Hassan Harraz
hharraz2006@yahoo.com
Hassan Harraz
hharraz2006@yahoo.com
Hassan Harraz
hharraz2006@yahoo.com
Garnet classification scheme

10. STRUCTURE
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12. Almandite
Fe3Al2(SiO4)3
S.G. 4.09 - 4.31, Average = 4.19; Hardness 7-8
Color Brown, Brownish red, Red, Black,
Black red.
Fluorescence None
Ca3Al2(SiO4)3
S.G. 3.42 - 3.72, Average = 3.57
Hardness 6.5-7.5
Color Brown, Colorless, Green,
Gray, Yellow.
Fluorescence None
Grossularite
Andradite Ca3Fe2(SiO4)3
S.G. 3.8 - 3.9;
Hardness 6½ - 7½
Color Green, yellow,
orange, reddish-
brown,
brown, black
Fluorescence not
reported
Pyrope
Mg3Al2[SiO4]3
S.G. 3.5 - 3.6; Hardness 7.5
Color Blood red, orange red,
purple red, pink, or black red
Fluorescence not reported
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Garnet Group of Minerals

13. End-Member Compositions of the Common Rock-Forming
Garnets
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Nesosilicates: Garnet Group
Complex solid solution with the following end-member compositions and their
characteristic colors:

15. PHYSICAL PROPERTIES
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OCCURENCES

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Garnets Color Explained

18. GEM VARIETY OF GARNET
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Garnet Group of Minerals

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21. 21

22. USES OF GARNET
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23. USES OF GARNET
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26. CONCLUSION
❑Garnet group of minerals is one of the
important group of minerals.
❑Since they are found in wide variety of
colours, they are also used as gemstones.
❑Garnet group of minerals are also
abrasives and thus have various industrial
applications.
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27. REFERENCES
• Dana, Textbook of mineralogy,4th edition, CBS
Publishers, 591p.
• Perkins Dexter, Mineralogy, 3rd edition, PHI Learning
Private Limited, 338p
• Karr P.F, Mineral optics, 353p.
• www.googlesearch.com.
• Edward S. Grew; Andrew J. Locock; Stuart J. Mills;
Irina O. Galuskina; Evgeny V. Galuskin; Ulf
Hålenius(2013). Nomenclature of the garnet
supergroup. American Mineralogist (2013) 98 (4):
785–811. https://doi.org/10.2138/am.2013.4201
•
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