Glass, the solid liquid.... A hardened, crystalline substance made by melting together a mixture of sand, potash, soda, and lime. It is strong and fragile; solid and liquid; transparent and opaque. It can be all of these things, all at the same time - quite an amazing feat!
Because of this, glass is an amazing collectible. Many of the collectors I know have started out with a small piece of glass which contained memories that were dear to them. Something that is both beautiful and can hold beauty within it, is something to be treasured.