The milky appearance of milky quartz is caused by tiny inclusions of gas, liquid, or other minerals. These inclusions scatter light, giving the quartz its cloudy, milky look.

Here's a breakdown:

* Gas Inclusions: Tiny bubbles of gas trapped within the quartz crystal structure can scatter light, creating the milky effect.

* Liquid Inclusions: Similar to gas inclusions, liquid trapped within the quartz can also scatter light, contributing to the milky appearance.

* Mineral Inclusions: Small particles of other minerals, such as rutile or hematite, can also be trapped within the quartz, creating a milky effect by scattering light.

The more inclusions there are, the cloudier the milky quartz will appear.