Complex sentence: Some minerals, such as colorless silicate minerals, absorb little or no solar radiation, but act by indirect photocatalysis, i.e. by producing a reactive species which then participates in another reaction.
Split into simpler sentences: Some minerals, such as colorless silicate minerals, absorb little or no solar radiation, but may still participate indirectly in light-driven reactions. Indirect photocatalysis may occur via the production of a reactive species which then participates in another reaction.