Optical Microscopy and Micromorphological Terms for Thin Section Descriptions and Interpretations

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 Contents	Page
The Nature of Light	1
Light and Crystal Symmetry	1
Polarization of Light	3
Ploarized Light and Crystals	3
Behavior of Light in Minerals Refraction Birefringence Interferen ce Color	5
Optical Properties of Minerals	6
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 Criteria	13
Clay Minerals	17
Soil Structure and Fabric	20
Misidentification of Minerals	21
Applications of Micromorphology	22
Describing Thin Sections	23
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-Matrix	30
Plasmic Structure	30
Pedological Features	31
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 al	56
Soil Microscopy and Micromorphology (FitzPatrick, 1993)	57
Matrix Components Other Definitions	57
Properties adn Features in thin Sections	59
Selected References - Optical Mineralogy and Micromorphology	62

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.

PETROGRAPHIC CONCEPTSOptical Microscopy and Micromorphological Terms for Thin Section Descriptions and Interpretationsentation

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