Cooperative Extension Service

PETROGRAPHIC CONCEPTS
Optical Microscopy and Micromorphological Terms for Thin Section Descriptions and Interpretationsentation


by Richard Drees
Soil Science Society of America, Soil Micromorphology Workshop
October 31, 1997


Table of ContentsPage
The Nature of Light1
Light and Crystal Symmetry1
Polarization of Light3
Ploarized Light and Crystals
3
Behavior of Light in Minerals
Refraction
Birefringence
Interferen ce Color
5
Optical Properties of Minerals6
Minerals Through the Petographic Microscope
Plane Polarized Light
7
Cross Polarized Light
8
Circular Polarized Light
10
Reflected Light
Petrographic Studies
11
Mineral Identification
Trasmitted Light (Plane- Polarized)
12
Trasmitted Light (Cross- Polarized)
13
Useful Mineral Differentiation Criteria13
Clay Minerals17
Soil Structure and Fabric20
Misidentification of Minerals21
Applications of Micromorphology22
Describing Thin Sections23
General Descriptive Criteria
Description Scquence
24
(Common Terms and Definitions from Three Basic Micromorphology Texts)
Fabric and Mineral Identification of Soils (Brewer, 1976)
Concepts of Structure and Fabric
26
Principles of Fabric Analysis - Distribution Patterns
Distribution Patterns
28
Units and Levels of Organization
Voids
29
S-Matrix30
Plasmic Structure
30
Pedological Features31
Cutans
31
Glaebules
Crystallaria
32
Subcutanic Features
Pedotubules
33
Handbook of Thin Section Description (Bullock et al, 1985)34
Basic Concepts
35
General Descriptive Criteria
36
Microsturcture
43
Void Areas
44
Types of Microstructure
46
Basic Components
Groundmass and Micromass
47
Birefringent Fabrics
48
Pedofeatures
50
Six Groups of Pedofeatures
53
Cross Reference Between Terms of Brewer and Bullock et al56
Soil Microscopy and Micromorphology (FitzPatrick, 1993)57
Matrix Components
Other Definitions
57
Properties adn Features in thin Sections
59
Selected References - Optical Mineralogy and Micromorphology62

This notebook is not intended as a text on optical mineralogy or soil micormorphology. It is intended as a supplement to more established texts or as a quick reference guide. Two of the common reference texts on soil micromorphology (Brewer, 1976 and Bullock et al, 1985) are currently out of print and difficult to locate. thus more emphasis has been given to these references than to the book by FitzPatrick (1993) which is currently in print and more readily available.



This page (http://www.ces.ncsu.edu/plymouth/programs/drees2.html) created by
Vera MacConnell, Research Technician, I on October 26, 1997.
Last Updated on February 5, 1998.