Here's why:

* Transparent: Glass is known for its transparency, allowing light to pass through it.

* Fusion Product: Glass is formed by melting and fusing inorganic materials (like silica sand, soda ash, and limestone) at high temperatures.

* Rigid State: Once cooled, glass becomes solid and rigid.

* Non-crystalline: Unlike crystals, which have a regular, repeating arrangement of atoms, glass has a disordered, amorphous structure. This is why it's referred to as a "supercooled liquid."

So, the combination of these characteristics makes glass the perfect fit for your description.