An Abbe diagram plots the Abbe number against refractive index for a range of different glasses (red dots). Glasses are classified using a letter-number code to reflect their composition and position on the diagram. Data plotted from the Schott Glass catalogue.
<a href="https://en.wikipedia.org/wiki/User:DrBob" class="extiw" title="en:User:DrBob">Bob Mellish</a>
CC BY-SA 3.0
<a href="https://en.wikipedia.org/wiki/Image:Abbe-diagram.png" class="extiw" title="en:Image:Abbe-diagram.png">en:Image:Abbe-diagram.png</a>