Charles Bray's Dictionary of Glass is a book that I wish I had added to my collection a long time ago.
This book is more of an encyclopedia than a dictionary. Entries are often paragraphs (or even pages) long and are generously illustrated (mostly in black and white).
Bray does an excellent job drawing the boundaries of what belongs in a reference book on glass when so many relevant topics are not necessarily glass-specific. You'll find both a lengthy entry about the structure of glass as well as an excellent short and relevant paragraph on vermiculite.
If you want to know what a ball mill is and -- more importantly -- what you'd do with one, you'll find it here. Want a better understanding of iridescence? Bray covers three techniques used to produce the effect (reducing flames, fuming and lusters). You'll also find the best tutorial on electrical elements that I've seen anywhere.
The of Dictionary of Glass was originally published in 1995. A second edition followed in 2001. It is published by A & C Black (London) and the University of Pennsylvania Press (Philadelphia). ISBN: 081223619X.
About Charles Bray (from the book jacket): Charles Bray is a well-known glass artist whose work appears in most of the major glass collections in the UK, Europe and the US. He is retired head of the Glass and Ceramics programme at the University of Sunderland. He is a fellow of the Royal Society of Arts and the Society of Glass Technology.