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 composed of 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.

Elemental Dust Composition Using Alpha-Particle X-ray Spectrometer ^[1]
Molecule	Chemical Name	Average Martian Soil by %	Uses
SiO2	Silicon Dioxide	45.41	Glass
TiO2	Titanium(II) oxide	0.90	Paint & cosmetics
AlO3	Alumina or aluminum oxide	9.71	Ceramics
FeO	Iron oxide or rust	16.73	Iron & Steel
MnO	Manganese(II) oxide	0.33	Fertilizer & food additives
MgO	Magnesium oxide or magnesiae	8.35	Antacid & alloys
CaO	Calcium oxide or quicklime	6.37	Cement, paper, steel
Na2O	Sodium oxide	2.73	Glass & ceramics
K2O	Potassium oxide or pure potash	0.44	Fertilizer, glass, soap
SO3	Sulphur trioxide	6.16	Sulphuric acid
Cl	Chlorine	0.68	Chemical processes as a strong oxidizer
	Total	97.81	Remainder unidentified

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.