The garnet group

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
(Ca
3Fe
2Si
3O
12)
Hassan Z. Harraz
[email protected]
Spring 2018

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

3. INTRODUCTION
3

4. 4
CHEMICAL COMPOSITION of GARNET GRoup

5. 5

6. 6

7. 7

8. The Garnet Group
Almandine
Grossular
Andradite
8

9. 9
Hassan Harraz
[email protected]
Hassan Harraz
[email protected]
Hassan Harraz
[email protected]
Garnet classification scheme

10. STRUCTURE
10

11. 11

12. Almandite
Fe
3Al
2(SiO
4)
3
S.G. 4.09 -4.31, Average = 4.19; Hardness 7-8
Color Brown, Brownish red, Red, Black,
Black red.
Fluorescence None
Ca
3Al
2(SiO
4)
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
Ca
3Fe
2(SiO
4)
3
S.G. 3.8 -3.9;
Hardness 6½ -7½
Color Green, yellow,
orange, reddish-
brown,
brown, black
Fluorescence not
reported
Pyrope
Mg
3Al
2[SiO
4]
3
S.G. 3.5 -3.6; Hardness 7.5
Color Blood red, orange red,
purple red, pink, or black red
Fluorescence not reported
12
Garnet Group of Minerals

13. End-Member Compositions of the Common Rock-Forming
Garnets
13

14. 14
Nesosilicates: Garnet Group
Complex solid solution with the following end-member compositions and their
characteristic colors:

15. PHYSICAL PROPERTIES
15

16. 16
OCCURENCES

17. 17
Garnets Color Explained

18. GEM VARIETY OF GARNET
18

19. 19
Garnet Group of Minerals

20. 20

21. 21

22. USES OF GARNET
22

23. USES OF GARNET
23

25. 25

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.
26

27. REFERENCES
•Dana, Textbook of mineralogy,4
th
edition, CBS
Publishers, 591p.
•Perkins Dexter, Mineralogy, 3
rd
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; EvgenyV. 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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