INTRODUCTION

Ternary System #1 - An-Wo-Sp System

System 1 - Anorthite - Wollastonite - Sphene System

This is a simple ternary system, with no solid solution, exhibiting a single ternary eutectic. Along the edges of the triangle there exists a binary eutectic in each of the simple binary systems, e.g. Wo-An, Wo-Sp and An-Sp.

The three components which define the system are:

On the image above note that the liquidus surface slopes down from each apex of the triangle towards the eutectic inside the diagram. Any liquids present in the system and which undergo crystallization will travel down the liquidus surface towards the eutectic. On ternary systems we will be tracing out the path the liquid follows, and as we will see it is possible to predict the path any liquid will follow during crystallization.

Remember you are looking at a map of the liquidus surface so that the fields present are labelled as a solid + liquid, e.g. Wo + L. The cotectic boundaries, shown in purple, separate the individual fields from each other. The isotherms are labelled in red and marked as dashed blue lines.