Liquid oxygen doesn't come from a specific source like a mine or a well. Instead, it's created through a process called fractional distillation.

Here's how it works:

1. Air is collected: Air is taken in from the atmosphere.

2. Air is compressed: The collected air is compressed to increase its density.

3. Air is cooled: The compressed air is then cooled to a very low temperature, usually around -200°C (-328°F).

4. Fractional Distillation: The cooled air is passed through a distillation column. As the air warms up, different components separate based on their boiling points. Since oxygen has a higher boiling point than nitrogen, it condenses first and is collected as liquid oxygen.

Essentially, liquid oxygen is a manufactured product derived from the readily available resource: air.