On his website Dress, Jewels, Arms and Coat of Arms: Material Culture and Self-Representation in the Late Middle Ages, Gerhard Jaritz has posted a manual of basic information on medieval jewelry and ornamentation.
The manual was created "in the course of various cultural heritage-projects at the Department of Medieval Studies at Central European University, Budapest."
The website offers photos and information on costuming, heraldry, armor and jewelry as used in the Middle Ages. From the preface:
The purpose of this manual is similar: to show how the emerging self-consciousness of the Late Middle Ages tried to represent and define itself in objects. Of course, the fashioning of human identity was already a common process in the Classical Antiquity: "Such self-consciousness had been wide-spread among the elite of the classical world, but Christianity brought a growing suspicion of man's power to shape identity." (Stephen Greenblatt) Augustine said: "Hands off yourself: try to build up yourself and you build a ruin." In this aspect the Late Middle Ages, but in some cases already the High Middle Ages have brought along a change. The representative members of the society, whose circle gets bigger and bigger, start to fashion themselves according to ideal patterns: from the idea of Christian ruler it descends to the courtly lover, to the knight and finally to the bourgeois. The self-fashioning consists not only of manners and taste, the internal adornment of the man, but also of external, bodily ornaments, which express the belonging of their possessors to a certain part of the society.