Here are some examples:
* Opal: Opal's beauty comes from the way light scatters off randomly arranged silica spheres.
* Obsidian: This volcanic glass forms when lava cools too quickly for crystals to grow.
* Amber: This fossilized tree resin is an organic polymer with a random arrangement of molecules.
* Coal: This fossil fuel is made up of a complex mixture of organic compounds, lacking a consistent structure.
* Pearl: While pearls are formed by living organisms, their primary component is calcium carbonate, which in this case, is not crystalline.
It's important to note that some minerals might exhibit both crystalline and amorphous phases, depending on their formation conditions.
