What does mean primary in geology ?

In mineralogy, a primary mineral is a mineral resulting directly from a major geological process (crystallization of a magma, diagenesis, metamorphism, hydrothermalism, etc...) and not having undergone the effects of an alteration subsequent to its deposit, such as surface oxidation for example. Pyrite is usually a primary mineral, which is transformed into goethite, a secondary mineral, by superficial oxidation.

In volcanology, we call "primary" a magma directly resulting from the fusion of its source rock before it has had time to undergo any differentiation or fractional crystallization.