Dust

On Earth, dust is washed out of the air by rain, and is cemented together to form rocks, or deposited as mud. On Mars, this does not happen, and dust is blown about for long periods. Dust Storms distribute this dust world wide.

Dust particles are very small, called 'fines', and would irritate human lungs (even if the dust didn't contain perchlorates, which are poisonous).

Dust Composition

The Martian dust is weathered from primarily volcanic rocks. This can be from mechanical weathering of basalts. But when basalt weathers in water if forms feldspar, and some dust is composted for feldspars.

Volumetrically Martian dust is dominated by composites of plagioclase feldspar and zeolite.

A small percentage of the dust is from powdered salts, of which the most dangerous is perchlorate ClO-4, which is toxic.

Dust Size

These are generally very small, only 3 micrometers in diameter. This is so small it will enter lungs and irritate them, being difficult for the cilia to remove. Good dust filters will be wanted in a Martian base, and waterfalls and pools may be wanted to help remove dust that enters a habitat.

Dust this small will wear moving parts. Any moving parts outside must be carefully sealed to prevent dust from getting into the joints.