OPTICAL CRYSTALLOGRAPHY

OPTICAL CRYSTALLOGRAPHY

I. INTRODUCTION

I.1 Properties of light

I.3 The polarising microscope

I.3.1.Orthoscopic and conoscopic viewing

I.4 Refractive index

I.4.1 Estimating refractive index using relief in thin sections and solid particle samples

I.4.2 Determination of refractive index relative to index liquid and other media

I.4.3 Dispersion of light: coloured Becke lines

II. PROPAGATION OF LIGHT THROUGH ISOTROPIC AND ANISOTROPIC MEDIA

II.1 Introduction

II.2 Refraction in anisotropic media

II.4 The indicatrix of uniaxial crystals

II.5 Determination of vibrational directions and magnitude of the refractive indices from the indicatrix

II.5.1 Introduction

II.5.2 The elliptical section

II.6 Interference colours

II.6.1 Monochromatic light

II.6.2 White light

II.7 Birefringence

II.8 Anomalous interference colours

II.9 Orientation of the elliptical section; the gypsum plate

II.10 Biaxial minerals

II.10.1 The wave-surface of biaxial crystals

II.10.2 The biaxial indicatrix

III. ORIENTATION OF THE INDICATRIX

III.1 Relation between the crystal structure and the orientation of the indicatrix

III.2 Extinction angle: parallel and inclined extinction

III.3 Elongation

III.4 Dispersion of extinction

IV. CONOSCOPIC RESEARCH

IV.1 Microscope set up

IV.2 Interference figures of uniaxial minerals perpendicular to the optical axis

IV.3 Interference figures of biaxial minerals perpendicular to the acute bisectrix

IV.4 Determination of the angle between the optical axes

IV.5 Interference figures of biaxial minerals perpendicular to an optical axis

IV.6 Centric interference figures with out of view moving isogyres

IV.7 Dispersion

IV.7.1 Introduction

IV.7.2 Dispersion of the optical axes, type I

IV.7.3 Dispersion of the indicatrix axes

V. OTHER OPTICAL PROPERTIES

V.1 Pleochroism

V.2 Optical activity

V.3 Linear, elliptic and circular polarised light