This crazy quilt is made from weighted silk - very common in the 1800s. Silk was sold by the lb. and in order to make it weigh more it was treated with metallic salts. Unfortunately overtime it damages the fibres.
This is the finished repair. It's the kind of repair that would be used on a precious or significant textile where it is important to salvage and maintain as much of it as possible.
Since this quilt top has no special significance (other than I like it and think it's charming) and was only used as a training piece, the rest of the damaged pieces were removed and will be replaced with new cotton squares - an equally valid repair for this type of textile.